Managed code developers that do not care about performance are just not developers.
Thats why every day real developers have headaches because some monkeys thought "hey dude ill just make this work and go home to have a banana, because its just managed code".
A good developer assures that the job he does is a well done job, else try another job, so we will all be more happy.
PS: .NET can be made even more perfomant and bug free, of course that will require more work and many people are just to lazy and most of them never used an unsafe method for example if that would have produced a gain in performance. (my opinion ).
In future of .NET languages i hope there will be more posibilities that tend to the power of C/C++, so you can explore the performance part also, that would give .NET a boost advantage over other languages.