I bought a hd5850 because mining is still profitable. it might not remain so for much longer though because the difficulty has been ramping up severely. obviously over time in should reach an equilibrium based on electricity/component costs.
I bought four hd5870s but was only able to run two because of heat issues. I took it down to install liquid cooling, which is having a bunch of snags, and the downtime has cost me dearly :-( Fortunately, I made a decent stash while the two were running.
There seems to be quite a bit of a Bitcoin interest around here, with several articles about it already: [1 2 3 4 5 6 7]
I propose that links and generic Bitcoin comments should be posted here, instead of making a new discussion thread for each interesting article about the subject.