The difficulty curve raises by 10% per week, or even faster. Two months ago I was thinking about purchasing a few 7950, because they would make a profit of a few BTC per month. For today they would barely return in a year period, even if the difficulty would stay on todays' level.
So as for me - I'm switching to LTC. I've tried this today, but I've overclocked my memory clock and the system hanged... and as I was doing it by a remote desktop, I couldn't access it by tomorrow morningm so I have no idea if it is more profitable than BTC for this moment