I've been enjoying 5.1.1 Untethered for a while (Old bootrom 3GS of course), and I've got to say that it's worth the jailbreak.
When I bought my 3GS I was unaware of the old bootrom vs. new bootrom stuff - and of course I have the new bootrom.
I'm still waiting on the ultrasn0w update. There seem to be sporadic issues with the available ultrasn0w fixer.