I haven't tried any of the BSD's yet, unfortunately, because the machines are at work and I have to actually Get Stuff Done.
Linux on the PA-RISC processor may be swell, but I've yet to see an actual full distribution. I know that Debian was working that way, but I haven't checked up on it in nearly a year, simply because they were so far behind that I didn't think I'd ever get a chance to actually do it. Ideally, Slowaris would be ported to HP hardware and all would be happy
Unfortunately, that's not going to happen. I've heard good things about NetBSD on PA-RISC hardware, however. Like I said though, we only have some 6 usable HP boxes and I don't have the liberty to blow one away and try Linux or NetBSD on it "just for kicks".
It's in that interest that I've been looking at picking up a cheap B-180L off eBay or something, but I've yet to come across any decently recent hardware at decent prices. The government may have $5,000 to spend on a HP-UX box for us to develop on, but I don't have that kind of money to (potentially) waste after I get a box and realize I can do nothing useful on it.