I have used a lot of different sites, some which sell the russian version require a one-off VPN activation. (dead easy, VPN on, start steam, activate code, close steam, disconnect vpn, restart steam, done)|
Never had any problems and all versions worked flawlessly.
The only difference between sites apart from price is delivery time. Some deliver within a couple of minutes, some an hour and some 2-3 days.
Just to add, it's not illegal in any shape or form as you are buying a legitimate download copy. (Notice that these are offered for Origin, Steam, uplay etc). No Steam bans to be afraid of.
Edited by Gunzberg at 23:10:44 08-06-2013
Steam/PSN/XBL/Nintendo ID/Uplay/Origin: Gunzberg
Blizzard Battletag: Gunzberg#2718