Building a 4x 7950 rig would be ~$2000, give or take, would hash ~2Gh/s, and would take about 6 months to pay off at the current difficulty. But we can probably expect the difficulty to be up by 50% in six months, if not more. If I could build it for ~$1000 it would make a better cost proposition, but at twice that it's not very effective against $300 5Gh/s miners coming online now.
Same here... I'm targetting the services industry rather than mining or trading; hoping to get a few more games etc online
Are you guys not doing it because of the initial cost for building GPU rigs or because of the looming threat of ASIC? I made my first two rigs last month, one with four 7950s and one with two 5970s. They've been pumping out about 4gh/s and I've made about 4 BTC. Subtract the cost of electricity and one of the 7950s has paid for itself already. I also didn't have all the cards up and running on the same day, more like a week in between the first and last two 7950s. I expect this month to be a little better.
No. I have determined that, for myself, it's cost-prohibitive and would probably not net any profit.
So, anyone building some new rigs?
Same here... I'm targetting the services industry rather than mining or trading; hoping to get a few more games etc online
Are you guys not doing it because of the initial cost for building GPU rigs or because of the looming threat of ASIC? I made my first two rigs last month, one with four 7950s and one with two 5970s. They've been pumping out about 4gh/s and I've made about 4 BTC. Subtract the cost of electricity and one of the 7950s has paid for itself already. I also didn't have all the cards up and running on the same day, more like a week in between the first and last two 7950s. I expect this month to be a little better.
While it's certainly not the most cost effective option, my rig with four 7950s cost around $1600 and is hashing at 2.5Gh/s. This certainly beats buying a grossly inflated "queue" unit from someone that may or may not end up shipping. And honestly, my end state was just to test out bitcoin and have my equipment pay for itself. Nothing like getting "free" video cards while you're at work.
, BFL ships their mystery boxes and Avalon units all get to their owners. As of right now though, I still see profits if the value of BTC holds/increases. 
