.NET, being truly Object Oriented, tends to lead people into the OO swamp. If you can avoid that, you can get better performance from .NET than from a similar VB6 program. I only have one good head-to-head comparison (and I don't even have that, anymore, because I can't find the old VB6 version of the program), but that one comparison was quite the comparison, as it took days to run without any user supervision.

On the other hand, I took over a project where I got to see how my predecessors were headed right into the swamp with enthusiasm and energy, as always seems to happen. Classes stacked on classes in arcane heirarchies that would eventually turn into an abysmal nightmare for maintenance.