Netscreen 5GTs will also do IPv6 with some ScreenOS 5.4 code revs (5.4.0r10.0 for sure). Those pop up on Ebay for $60ish and make respectable home CPE devices. Not quite the horsepower of the SSG5 but they seem to hold up reasonably well.
Dan Jones
Having significant experience with all three products, I will strongly suggest
going with the SRX-100 if at all possible. It's real JunOS, even if it does take
a bit of bludgeoning to get it to stop impersonating a netscreen security model.
It's the same price the NS5GTs used to sell for ~$5-600 (512MB/1G) and has
a great deal more to offer (like fully functional routing protocols and JunOS
configuration environment).
Most of the NS5GTs I ever deployed in always-on environments didn't last
more than about 3-4 years. The SSG-5s I've dealt with haven't started
dying yet, but, most of them are only about 2 years old.
Owen