I own one and love it. I think playing a QS8 is comparable to playing a real piano, plus it's always in tune. Mine has toured all over in a SKB road case for years and never had an issue.
$475 seems to be about what they go for on ebay, but I'd offer $375 as the market for a keyboard like the QS8 is way down right now.
There are no speakers built into the QS8 - you'll need an amp/speakers(s) or headphones.
I can't compare it to anything else you could purchase because I'm not familiar with currently manufactured keyboards such as Yamaha and Roland etc. The QS8 is a very fine instrument, but probably a little dated.
As much as I love mine I wonder if it's the best pick for you. I can't believe I'm about to recommend a Casio, but they offer 88 weighted keys and built in speakers for under $300 brand new. That's quite a bit less than a used QS8. I could never tour with the Casio, but if you're just starting out or whatever, the Casio or similar may be more suitable to your situation.
Hopefully Skip, Goz, and Burn will check in on this post and offer better advice, but then again, I can say that I really love my QS8.