PokerStars is the largest poker site in the world, offering massive volume in cash games and tournaments 24 hours a day. It sets the standard in the industry for tournaments as well with an unmatched selection and sit-and-gos at all stakes starting up virtually every second.
The software is also top-notch and offers fast play, high reliability, great multi-table options and a lots of customization - it pretty much sets the bar for the industry there as well.
If you're looking for a downside, though, it's probably the inconsistent competition. Because of the huge player base, the opposition can range from super soft at one table to unbelievably aggressive just the next table over. Lower limits and tournaments are still flush with bad players but there are literally thousands of strong players trolling PokerStars daily looking to make a living, so expect some tough competition scattered throughout your games.
If you like more obscure poker variations, PokerStars is for you with a wide spread of games offered - Texas Hold'em, Omaha and Seven-Card Stud in all versions, H.O.R.S.E., H.O.S.E., 2-7 Triple Draw, Five-Card Draw, Razz, 2-7 Single Draw Lowball, Badugi, 8-Game, Mixed Hold’em and Mixed Omaha Hi/Lo. By the time you read this, they've probably added more.
It's worth noting that PokerStars has one of the best loyalty programs in the world and players who achieve the coveted Supernova status get free entry into $1 million tournaments, insane frequent player point multipliers and various cash bonuses. Everything about the PokerStars loyalty program is world-class including the frequent player point store, which is the biggest in the poker industry.
Overall, PokerStars keeps its spot at the top of the industry by offering a real "feel for poker" and responding rapidly to player feedback. Bottom line, it's one of the best poker sites in the world and if the competition wasn't so tough at the higher stakes, it would be tough not to rank PokerStars higher.
Real-money player statistics as of September 2010 show 22500 ring-game players at peak hours and 155000 tournament players at peak hours.