They are good quality, with the only difference being the "sporter" stock, rather than pistol stock.
Pro Mag (which seems to have a bad rep, though I have had 0 problems with mine) makes a Saiga 30 rounder and I believe Sure Fire does as well. Just keep in mind that if you use these mags without converting, you will not be in compliance.
Check out the forums at saiga-12.com for more information than you can shake a stick at concerning all things Saiga.
This is true, but if you do use them, that's 3 fewer compliance parts you have to worry about. Personally, I'd put all the compliance parts in the gun itself, so I could use foreign-made mags.
The noise-to-signal ratio can be pretty high over there... proceed with caution and keep your BS filter turned up. I've been a member there since 2003, but have a whopping 378 posts. I visit infrequently and contribute even less.
922r compliance, any "non-sporting" rifle that is imported has to have a certain number of US made parts. I'm not familiar with the ins and outs of it, but that's the most basic definition.