Looking through the slides for this presentation. I found a few things interesting.
‘Server GC’ in .Net 4.5 now supports background garbage collection, so it is now more useful for desktop apps as well as pure-throughput apps. It also supports better distributing the mark phase of mark-sweep across multiple cores allowing garbage collection to scale better.
Profile guided optimization can now be done with managed code, and the resultant information annotated into IL for improved startup-time and reduced memory usage. Apparently.
On Windows 8 only, .Net 4.5 will ‘auto-NGen’. No need to think about whether you should NGen or not, its all automatically done in the background based on observed assembly usage.
And finally quite possibly my favourite. Profiler hooks can now rewrite methods and request a rejit. So you can inject instrumentation to methods which have already been jitted, or disable instrumentation without a process re-start.