Did you knew that the only correct way to view the content of GAC (as of .NET Framework 4.0) is by using gacutil –l command? Discovered that just now. My first reaction was "ORLY?". Microsoft must be joking but, no. Old good assembly folder indeed doesn't show all .NET 4.0 assemblies. ILSpy's (ILSpy 22.214.171.1240) "Open from GAC" also showed wrong results then searching assembly by name.
As I've discovered there are two GACs now, and this is the root of the problem. To complicate things more, there is two gacutil.exe (four if you count x86 and x64 versions) versions, one for CLR 2.0, and one for CLR 4.0.
Can't say for everyone, but searching some hundreds assemblies thru a console output of seems like a not very convenient work. That's an odd, strange behaviour for such developer oriented company as Microsoft. So currently I'm in search for good universal utility which will provide convenient interface to manage this GAC mess. I'll update this post if there will be any progress in this quest.
Update. Here is my discussion about gacutil.exe on StackOverflow.