Our market niche is high-end computing, and always has been. In the x64 world, it means that in order to compete we have to do stuff that white boxes can't.
My experience always had IBM P5 (now P6) for the real high end applications, except for big Oracle servers. We primarily used SPARC for mail, Oracle, and webservers, or the specific telecommunications app that required Sun. On the other hand, I know the defense department still has a lot of high end SPARC, due to trusted Solaris.
I really hope SPARC does survive,and, as I said, I still prefer Solaris as a Unix OS. But I would like to see it as more than just an Oracle niche support market. I'm just not convinced that it will happen. Especially given the crap outsourcing that Sun has taken to for their support contracts. Hell, I know more about their new hardware than most of the CEs that have been sent out to support the limited Sun hardware at the currently company I work for. And that crap support is the reason that there won't be much more Sun coming in here.