Personally, I've had fine luck with them. I bought an el-cheap-o Epson printer when I was in college because it was a huge PITA to try and print stuff off on the communal dorm printers. I've used generic ink in it as long as I've had the printer. I've bought it all from megatoners.
Sometimes it leaves little "clumps" of ink on whatever I print. This printer is nothing fancy at all, I use it for quick printing if I need something in a hurry or I want to save a bank statement or something. The cartridges occasionally stop working (and dry out I assume), so I just swap in a new one (black carts are like $1.50 each or less).
There is another vendor that sells generic ink, saw a post in Hot Deals about them. I've never tried them personally, as I'm sitting on a stockpile of generic cartridges for my printer now.
Here's the thread about SwiftInk:
http://forums.anandtech.com/messageview.aspx?catid=40&threadid=1514424