Hi GL developers,
nvidia has released a profiling kit for windows called “nvperfkit”.
I have opened a thread at
http://www.nvnews.net/vbulletin/showthread.php?t=54445
where you should post if you are interested in that tool for linux!
I talked to one of the developers at SIGGRAPH today, and apparently they’re planning to add support for Linux to it for the next release, which is probably going to be close to the end of the year. There also seem to be plans to add better introspection capabilities for the drivers, to give more direct feedback about things that can make your program go slow. Everything without guarantees, though, but it looks like nVidia is putting some effort into Linux support now.
Go nVidia! 
Thanks for the infos, Dirk.
An nvidia guy now told me: “Yes, we are targeting NVPerfKit 2.0 to include linux support. This will hopefully be available this fall.”.
Another nvidia guy told me “We are investigating Linux support for NVPerfKit but do not have firm plans for release yet.”
So, it seems nvidia is thinking about a profiler for linux, but the release date is not yet clear. If their drivers are done platform independently, the development of such a profiler should be rather easy. It all depends on the amount of demand for a profiler by the potential users. We should tell nvidia that there is a great demand for it!