managed to check out a SunBlade100 this week, and it works very well and easy, as long as you're able to find out how to get to the OK-prompt
BTW: In my experience reiser on sparc (gentoo on a v240, s/w raid5 and lvm2) is extremely unstable! I reverted to ext3. Unstable as in Kernel panic! So be carefull when developing with reiser tools.
I developed SystemRescueCd-sparc on SunBlade-1000 with Reiser-3.6 and I had no problem. I prefer Reiser to ext3 for its efficiency with small files (a lot faster and less space wasted).