To my eyes it looks like BAA did a decent job with the changes. They raised the bar, which is a good thing, but not too much which keeps the bulk of runners in the game. They also put it somewhat on runners to run their best time in order to be able to get in earlier. I'm going to predict that we see a lot less times within 1-2 minutes of the qualifying standards. In the past I suspect runners, in some cases, did just enough to get the standard. Under the new policy you'll need to significantly exceed the standard to get yourself into one of the earlier registration pools.
For the 2012 marathon, the September 12-23, 2011 registration dates put the fall 2011 marathons in a bad place (i.e. on the outside) but this is really only a 1 year issue because for 2013 runners will be able to use their fall 2011 results to qualify.
I like that they included a provision for 10+ year Boston finishers. As long as those runners hit the standard they can register starting on trhe first day it opens. They say there are only about 500 in that group.
Would have liked to see them tighten up the women's standards a little but that was a no-win situation for them. If they had, you'd have heard charges of sexism from certain parties. If I'm BAA I'm probably saying to myself, leave that one alone.
I agree that it will be challenging for the BAA to verify the "20 minutes under the standard" in just 2 days before the "10 minutes under the standard" kicks in. There may not be that many entrants (relatively) at the "20 minutes under" point, but at "10 minutes under" I bet you have a lot of entrants. And at "5 minutes under" you will have a ton of the field. BAA only gave themselves a 3 day window to deal with that processing before regular entry opens. Good luck to them!