I had a Sun Netra T1 200 for a bit over 10 years that ran Debian on Sparc. The hardware was reliable, the Debian as an OS worked well enough, less of a headache than Solaris IMHO. Occasionally had some weird kernel related quirks, but I generally just kept it tracking Debian sid.
I think it was just a matter of time that the Debian sparc port went away, the surplus of old sparc boxes has gone away more than anything. I'm not sure anyone used Debian on sparc for anything serious(read business use), though.