I would imagine Quake would run like crap. Sun is the laughing stock of the computer industry. This is the end of the line with regards to the SPARC series (which was flawed to begin with).
Hmmm, I think this is the end of the old SPARC. I think the SPARC is a a good example of a "Theoretical Processor", as Linus would put it. In theory the SPARC is a wonderful design (well I like it... :-) ), but in the real world it suffers because real software isn't and can't be perfect.
It's much like the Itanic, in theory that thing should be forming some kind of "Skynet", but in the real world my ZX81 gives it a good run for it's money :-D
Sun are switching to the Opteron now. I totally believe in that thing, it's an Alpha (AMD did hire the Alpha design team to design it!) with an x86 emulator stuck on the front for the 32bit stuff :-P (I know painfully simple metaphor, but it works).