This means just as the release notes say that Monotouch now figures out how many trampolines to allocate.
To add more trampolines you add compiler flags such as:
-aot "nrgctx-trampolines=4096" -aot "nimt-trampolines=4096" -aot "ntrampolines=4096"
Usually when you were running out of trampolines meant that you were using a lot of generics and interfaces, which are hard to calculate how much memory needs to be allocated for ahead of time (aot). So Xamarin must have found a magic way to do this calculation and allocate the trampolines accordingly. I couldn't find more information about this.
There's a bit more information about trampolines in general in this thread: http://forums.xamarin.com/discussion/503/trampolines-cost and this thread which was prior to the other one: http://lists.ximian.com/pipermail/monotouch/2012-March/008800.html