Ken Arnold posted about the problems with generics, namely that they substantially increase code complexity without providing commensurate benefits.
He's spot on - generics are the programming language feature that never should have happened, and I speak as someone who, when I was a heavy user of C++, loved generics. Even now I yearn for the elegant consistency of the Standard Template Library. But the points Ken makes from a Java perspective apply equally well to C++, and C# as well. That generics increase both the semantic and syntactic complexity of code is undeniable. Their benefit as a runtime type-checking mechanism does prevent - or at least help diagnose - certain classes of bug. But these bugs are not generally especially common, nor difficult to diagnose or fix in the first place. This can be seen quite clearly when considering that dynamic languages, which enforce no type checking at all, do not suffer in development effort nor code maintainability as a result - if anything, they demonstrate the converse.
One benefit that Ken doesn't mention is the use of generics to signal a programmer's intent - to make a collection homogeneous is, to a limited extent, to make it self-documenting. Again though, this benefit is small compared to the complexity costs.
When I started typing I thought I had more of a point. Ho hum.