I saw the thread [Re: Sample based profiling] on tech-userlevel@, I'm not subscribed to this list but I'm answering here because it's related to tprof among other things.
I agree that it would be better to retire gprof in base, because there are more powerful tools now, and also advanced hardware support (PMC, PEBS, ProcessorTrace). But in particular, it would be nice to retire the "kernel gprof". That is, the MD/MI pieces that are surrounded by #ifdef GPROF. This kind of profiling is weak, and misses many aspects of execution (branch prediction, cache misses, heavy instructions, etc) that are offered by tprof. I already dropped NENTRY() from x86, so KGPROF is officially not supported there anymore. I think it has never worked on amd64.