Lots of people could cover 1:02:31 these days. His final time was 2:07:56, but his last-half pace for a full marathon equates to only 2:05:02, very good, but probably not good enough to medal. Geoffrey Mutai ran 2:05:05 a couple of months later on a very tough NY course; he could certainly have covered. And frankly, from what I read the 2nd and 3rd place finishers at the 2011 worlds could have been a lot closer - if not actually challenged - had they not gone tactical to try and get second.
Not sure if London is any indication of what Makau can do. Dropping out was kind've a weird thing for him to do, unless he really had been given a guaranteed place, or was injured (and I haven't read anything to suggest he was). But in his career, he has never run a marathon in over 2:06:14, and he has four runs of 2:05:45 or better, including his 2:03:38 in Berlin in September, a few weeks after Kirui's win at the worlds. He has also run 8 halfs in less than an hour. This guy is only 27, and he has jets. He's also a winner. Other than his 3rd in London 2011, he's won every marathon he's started. Although granted, his performance at this year's Bupa run wasn't sterling.
I am sure that Boston 2012 is no indication of what Mutai can do. As I mentioned earlier, I was in that race, and it was brutal. But in the last couple of years GM has been consistently around 2:05 or lower, including a 2:03:02 in Boston (I guess you missed that w.r.t. PBs, although yeah, the weather was kind've 'special'), as well as that astonishing 2:05:05 in NY - I seem to remember Ryan Hall saying he didn't think that kind of time was possible on that course. And please, November 2011 was not that long ago.
Kirui, on the other hand, has never run a marathon sub 2:05, which Mutai and Makau have both done twice. His times have been a bit over the map. A couple of 2:06:50s, a DNF in last year's Virgin, a few 2:07s, a 2:13 in NY (2010). And other than the worlds, I can find only one other race he has won, Vienna in 2008.
Kirui is a very good runner, but in my opinion he has not shown the tools to cover a very fast pace.
Anyhow, I'll put up $50 that the Ethiopians will take at least two of the marathon medals in London, and that Kirui will place no higher than 5th.
Hell, I'll put up a grand if it'll help get Makau and G Mutai into Berlin this fall. Maybe even Geb - we keep writing this guy off, but I get the sense he has at least one more good run left in him.
Anyhow, this subject is depressing me. I think I'll try to find a Cam Levins thread to terrorize.