While I'm a Maemo / MeeGo supporter and not a big fan of WP7 I can understand the logic of his decision. This was really the lesser of two evils.

The problem for Nokia was that there was no way their current strategy would have been successful in any way / shape / form.

Symbian - Let's say they hit all of their S^3 and S^4 schedules. The problem here is that they'd only catch up to iOS 3 and Android 2.x by what next year? The bigger issue is that Symbian is phone ONLY!!! The industry has shifted and a tablet / mobile device ecosystem (post-PC era). At best Symbian is a solid phone OS which would have been fine 2 years ago but isn't going to cut it in the future. Why dump resources into something that has a big future. I don't see Symbian moving to tablets in any scneario.

MeeGo - Obviously this has both phone / tablet capabilities, but when? Best schedules show end of this year and early next year for the first devices also. By this time next year Apple / Google will be well into their mixed phone / tablet strategy where Nokia would only just starting with version 1.x which is iffy however you want to look at it. And according to OP this is if they hold to schedule which may not be the case.

Whether they choose Android or Windows they will still have a difficult time competing with the Samsung / Asus / HTC / Motorola so neither would be a sure win.

Right now Apple and Google comfortably share smartphone mindshare. I think there is room for a third player but is there room for a fourth? If MeeGo is going to succeed it needs to beat Windows and I don't think in any of the most aggressive and optimistic scenarios did they see MeeGo getting marketshare from Windows in the next couple of years.

For Maemo / MeeGo to have been the primary OS of choice for Nokia, and to be number 3 they would have had to make that decision 2+ years ago when they had the money and margins to double down on a future platform. OPK didn't have the vision or the dictatorial power of a Steve Jobs to make difficult decisions like that so Elop has to pick up the pieces. The guy has a tough job and I don't envy the decisions he has to make.