Party Poker 

Number Of Players: 50,000+ Party Poker is one of the larger poker rooms, so even less popular game types (like Omaha Hi/Lo) always have tables on the go.
Software: Party Poker offers a nice, clear download-only version with avatars. It's a quick download even on dial-up.
Bonuses: Constantly changing, please see Party Poker's site for details.
Deposit Options: Credit Cards, FirePay, ClearChex, Western Union, Checks, Money Orders and Wire Transfers.

Ridiculous bad beats on PartyPoker

Party Pokers software is very easy to use and offers some nice features. In the Lobby, it's very easy to find the game and stakes you are looking for. Party Poker has a "Hide Full Tables" option so you can choose to see just the tables that have available spots, or all tables. You can also sort the list by the size of the average pot, which is very important in your table selection strategy.

Party Poker's table game interface is not the prettiest to look at, the software is very stable and has some nice features, such as right clicking on your opponent and taking notes, and right clicking on yourself and seeing your session's statistics. When you take notes on an opponent, a little yellow sticky note appears on the corner of your opponent. If you sit down at a table, and some of your opponents have that yellow sticky note, then you know you've played with them before and have notes on them. Unfortunately, you must go through the extra step right-clicking on the opponent to read your notes. The statistics is also a nice feature, but the statistics only report for your current session, and you do not have control of keeping those statistics averaged over several sessions.
Betting is very easy on the no limit tables, there is a slider that you can use or a text box to type in your bet. The bet amounts and pot amounts show the actual dollar amounts under the chips so it is very easy to see the dollar amounts and calculate your odds.
There are three action buttons during play - fold, check/call, and bet/raise buttons. The buttons change depending on the action.
Party Poker does lack a good buddy finder (or fish finder). It would be nice to maintain a list of players to keep an eye on, and have Party Poker tell you what tables they are playing on. Party Poker's Buddy List will inform you if a certain player is logged in, but not where they are at.
Party Poker, like many other poker rooms, offers your hand histories, but you can only request up to 100 hands at a time, and they are emailed to you.
Since Party Poker is the largest poker room in the world, there is always plenty of action at just about all the stakes in all the games. Party Poker is constantly running 10 Player Sit-N-Go Tournaments and ring games. You can always find a seat to complete a full game, and if you don't like your table, it's very easy to leave and find another table immediately. Party Poker has the most action anywhere.