PokerStars is the worlds largest poker site by far.
In our opinion it is also the best. The only thing that is not so great is that the competition in general is tougher than on other sites and that can of course be a major issue.
If weak competition is high on your wanted list we recommend PartyPoker as the number one choice, see below.
Pokerstars also has the best software for playing on mobile devices.
Americas Cardroom accepts US players!
Out of the few sites that still allow US players Americas Cardroom seems to be the safest choice. Payouts still (February 2013) seems to be working fairly well within a couple of weeks which is way better than the competition.
That being said, caution is recommended and our advice is to regularly withdraw money and keep a minimum in your account.
Software and traffic is decent and although other U.S accepting sites might be a little bit ahead on this the ability to actually get money out from the site makes it our main recommendation for U.S players.
PartyPoker has great software, decent traffic and fishy players.
If you think the games is too tough at Pokerstars you should give PartyPoker a chance!