No matter how many features & benfits a poker room offers, it all crumbles down if there are no players. One of the key aspects of making money at an online poker room depends on the other players your playing against. You have to know who's good and who's not. It is also important to find a site with lots of players so you have a better chance of finding that game that is perfect for you.
The more people playing at an online poker room the better chance you have of finding the right game for you. Smaller sites may dilute the players in a game causing it to 'break up' prematurely.
Quality of Players
It is essential to recognise the types of the other poker players at your table, do your best to play on a table full of loose players. A good way to recognize this is to look at the table pot sizes and the percentage of players in on each flop (provided the poker room offer table stats).
Promotions are things that an online poker room may offer you to get you to play at their site over other sites. This could be anything that would attract you or give you incentive to play your poker there.
High Hand/Bad Beat Jackpots
Some poker rooms sights offer you cash prizes for getting high hands (straights & royal flushes) ranging from £250 to £500. Bad beat jackpots are award when a very strong hand is beaten (say full house beaten by a 4 of a kind), these jackpots tend to be massive between £2,000 to £30,000.
The competition between poker rooms is intense and most offer deposit match bonuses. You should expect a decent incentive for joining of at least 25% extra on your initial deposit.
There is nothing more frustrating than losing your connection to the poker room server in the middle of a hand. The good sites won't ever let this happen but it still does at some sites.
Some sites specialise in tournaments and others in standard ring games. many of the sites won't offer some for the less popular poker variants.
Obviously the better the graphics all the better, but the real difference lies in the layout & design, how easy is it to keep track of the face up cards, does it show the player's chip stack etc.
Some online poker rooms offer you access to stats so you can examine your past games (hands history), other sites will also give you access to table stats which is particularly handy in finding a a good table to play at.
The level of service provided by a poker room can vary a lot, but you should expect at least 24/7 support via email & telephone, some of the key areas which differ include:
Speed & quality of service
The key areas are obviously the speed and quality of service, it's often hard to find one let alone both.
Some poker rooms feature hosts which are allow you to chat live with a customer service rep
Although a separate section can be written about this, the payment & withdrawal methods do vary between sites. The better poker rooms will not charge for processing withdrawals but be aware many do.