As of today, I suspect that mining is not profitable any more, unless you already have the video cards. Honestly, I think it passed a couple of weeks ago.
If you buy hardware for mining, you will probably never make your money back...
I've made 10BTC the last month with a hashrate of ~70MH/s. I mine about 16h/day and have a 5850 to setup tonight which will run at approximately 300MH/s. It costed me to what equals about 150$ and considering I've made 10BTC the last month with ~70MH/s I should make about 3,5 times more at current difficulty. If difficulty would be the same for another month (It won't but still) I would make 35BTC which equals to 245$ at current exchange rate ($7/BTC).If you buy hardware for mining, you will probably never make your money back...
If difficulty doubles the next month I would still almost have to money to buy another card.
And if something goes wrong, I still get a decent GPU which I need. Besides, I can continue to use my old one for mining for even more profit.
I'm not interested in making $$$, just making a damn good GPU deal
Buy yourself a radeon hd 5870 card for about $200. With 350mhash/s you'll get 1.3 BTC/24 hours. That's 39 BTC/month. It's about $273 with current rate of 7 USD/BTC. Not counting electricity bills. Most likely the BTC exchange rate will go up after difficulty increase, so you'll get even more than $73 profit in return.
Guess someone beat me to the punch. Well, my calculation wasn't too bad anyways 