I use Flock daily. It's based on a not-so-up-to-date version of Firefox and I've seen at least a few "review-my-site" posts here where the site barfed catastrophically. I also use IE6 fairly often (mostly for testing though).
>> Do you know anyone that is still on a very old version
Yes. Most clients I work with either have employees on IE6 or need to support it for their users (usually both).
I use the development version of google chrome when I do use it but most of the time I use conkeror which is probably pretty dated when it comes to css and html 5 (not so bad but around firefox 3.0 ish with xulrunner 1.9)
Everyone I know who isn't computer savvy uses IE 6 on xp 7 on vista and 8 on win7 and so on for operating systems you choose.
Well, I'm reading / writing this using Chrome 6.0.447.0 dev, and the Firefox that's installed on this box is the FF4 beta candidate... so yeah, I guess I try to stay fairly close to the bleeding edge.
>> Do you know anyone that is still on a very old version
Yes. Most clients I work with either have employees on IE6 or need to support it for their users (usually both).