Asic/FPGA's? Or just GPU/CPU? Which currencies? I was one of those that mined a few blocks of bc and spent it all before it was worth anything, and then thought that fpga's and asics took it out of my price range. Have considered trying my hand at it again.
As a followup to this, the scrypt coins I mine increased in profitability this week. I'm making over 1% ROI per day right now.
Increasing difficulty is less of an issue for altcoins. There are so many of them that difficulty may spike on one but that will cause it to drop on others, shifting which is more profitable. They tend to self correct better than Bitcoin.
Edit: ROI could be improved a bit on this too since I intentionally bought hardware that was good to experiment with rather than optimizing ROI.