Four things I want to state explicitly before I get started:
1. All of this is simply my opinion. I am not claiming to know anything, it's just my interpretation. Please imagine "IMO"s all over it if it makes you feel happier.
2. I've never met Lawrence Miles and my abject fear of RL fannish socialising makes it staggeringly unlikely that I ever will. I have, on the other hand, read what must amount to millions of his words, between his novels, non-fiction books and articles, interviews, blog posts and associated blog-like things like the Countdown.
3. Although I enjoy Miles's writing, he's far from perfect. He's appallingly classist (with a nasty side order of fetishisation in there too) and quite sexist quite a lot of the time. It's very obvious that he's difficult to work with and he almost seems to delight in burning bridges with people initially well disposed towards him. There are many valid criticisms that can be made of him. I'm just trying to argue against a particular one that I think isn't valid.
4. I strongly disapprove of Internet psychiatry, so I'm not going to try and get into questions of whether the guy fandom more-or-less affectionately calls "Mad Larry" genuinely is mad. (Though if he is, the pointing and laughing gets a hundred times squickier for me, FWIW.)
I honestly believe that Lawrence Miles is a creative genius. He's one of those writers who throws away ideas others would build whole trilogies out of. And he keeps doing it, over and over again. (The key thing about Alien Bodies isn't all the arcs it launched -- which was an entirely accidental thing, AFAICS, but also inevitable in a range that was struggling to find a direction, that some of those brilliant ideas would resonate with the readers and the other writers -- it's that it's full of other ideas that never did get picked up on. And then Interference comes along and does a whole bunch of different stuff, only tangentially related. And Adventuress, again, launches a whole bunch of stuff without really trying.) Doctor Who fandom is lucky to have had him write one book for it, let alone several and a whole set of spinoff ranges.
Now, bearing in mind point 4, I need to be careful how I phrase this, but it definitely seems fair to say that Lawrence Miles has an outlook on reality that differs significantly from most people's. And I think both the successes of his creative work, and the misunderstandings that arise, stem from this difference. And that difference is that he sees, very clearly, the links between individuals, society, and the culture that mediates interactions between the two. My theory is that this view of the world gives him a skewed perspective where it's vitally important that the culture be vibrant and alive.
And so, for Lawrence Miles, the enemy is banality.
(Actually, now that I come to type that out, I'm going to have to digress for a short while. Because it's impossible for me as a Faction fan to write "the enemy is" with a straight face, even after all this time. But the thing is, it's the Great Houses who represent banality. The Enemy is the unknowable universe that we'd have if human creativity was unfettered. But then it's obvious you're supposed to be on the Enemy's side, even if that very unknowability is frightening ...)
This idea comes through in his work (even if you don't buy into my Enemy theory there). Although his best remembered brainchildren are Faction Paradox, the ones that come closest to expressing all this are the Faction's creations, the Remote -- colonies of humans who respond to transmissions in unpredictable ways (and so make the perfect way to mess up a Time War, as no one can work out how they're going to interact with everyone else that's going on). In The Book of the War, we learn about the "broken Remote", which as well being a good pun is a story of a Remote colony that were made predictable, and thus their threat nullified, by the Great Houses using banal transmissions which, when you read their descriptions, are clear satires of Ally McBeal and Big Brother. In Bad Wolf, Big Brother just kills you; in Faction Paradox, it makes your entire existence and that of your entire culture pointless.
It also comes through in Miles's position in that oh-so-middle-school fanwar of "rad" vs "trad". (For those of you lucky enough to have missed out, before Who fandom had The Eternal Shipwar, we had "debates" on whether the point of new Doctor Who was to be new new, or to be as close as possible to your favoured era of the TV show -- which usually turned out to be something the '70s.) People always seem to wonder what Miles's problem with Mark Gatiss is, as though it's going to turn out Gatiss was horrible to him at some point, or something. But really -- his problem with Mark Gatiss is that Mark Gatiss acts as though the point of new Who is to come as close as possible to recapturing the stuff he used to like in the '70s. That's why he's always banging on about Gatiss's PDA Last of the Gaderene, which actually succeeds on its own terms as a story that could come from late Season 10. I personally found it disappointingly dull; for Miles, it would seem, it's a moral failing of the worst kind to have such a horrendously limited aim in the first place.
It's also worth noting along the way that Miles is much more self-aware (and, in some ways, self-deprecating) than some people give him credit for, and he's also much more aware of what people are saying about him than he likes to admit. This latter is nowhere near new behaviour -- the Interference Rumour Table, the radw flounce, these are all the antics of someone who likes poking at things with a stick. Oh, and this isn't the first time he's moaned about Neil Gaiman, incidentally, given that that seems to be exciting the most interest from the FW crowd. (Though given his baleetion habits, I can't now find evidence of it.) I disagree with him on that -- I ♥ Sandman in particular VERY HARD INDEED, but from Miles's point of view it's another stunted creation that had the potential to be so much more. I think Lawrence Miles views unachieved potential as worse than no potential at all.
And he thinks that Doctor Who (his personal mythology, remember) has an infinite potential to be new, to be "surprising", to be anything but banal.
And this is the heart of his problems -- when he has them, everyone always tends to ignore his complimentary reviews -- with the new series in general and Moffat in particular. When he says things like the infamous "I could piss Blink in my sleep" comment, he's not saying "I am a better writer than Moffat, therefore I should be running things", he's saying "Blink failed to surprise me, failed to push the envelope of what the series could do sufficiently hard, and I think that Moffat could write something which did do that". In its way, it's a very backhanded compliment.
People seem to write these off with ideas along the lines of "oh, he's just bitter because no one's asked him to write for the new series". And I really don't think he is (maybe a bit miffed no one's asked him to do another book). He knows with his lack of TV experience and so on he hasn't got a hope. And I don't think he really cares, either. What he cares about is his desire for Doctor Who to be the ultra-rad thing he has convinced himself it should be, not that he necessarily be the one to write it. There's much less ego there than most people seem to read into it, to my way of thinking.
Now, I'm certainly not saying anyone has to agree with me about any of this. But hopefully you can see why I feel a profound sense of disappointment when people sum up the whole thing with what amounts to a "LOL, bitter".