I'm actually a big fan of the website. It's clunky and awful and there are tech issues, but damn it is such a fine price. I get albums in 320kbps AAC for about $2.00. It's changed the way I listen to music. I'm buying new albums all the time and hearing all sorts of stuff I otherwise wouldn't be able to find, and their selection is to my eyes superior to iTunes. I used to be someone who only downloaded music from P2Ps and yet I really prefer the Allofmp3 for the quality.
However, there are the obvious problems. The service is legal in Canada, but I still have the knowledge that my money is obviously not going to the artists. Now, I don't particularly like supporting a company that could very likely be construed as organized crime, but I also don't like supporting large music corporations that have behaved improperly. I think it comes down to a sort of moral issue and a practical one. The music that I get from that site is FAR superior to that on the iTunes store and superior to what most people have on P2P and at a small fraction of the price of iTunes. Whether or not they're morally right, you have to hand it to the guys that run the sight. They're ballsy and entrepreneurial as hell and they keep constantly updating and improving. So I'll give them my money. Why not?
Also, as far as sketchy credit card stuff, it's really not an issue.