PokerStars and SportsBook (Cake skin) were my first poker sites
. Starting out I liked SportsBook because it was easier to deposit from the US and they ran frequent reload bonuses. However their software does suck. Once my online game started improving I much preferred Stars (for cash) and later FullTilt for tourneys, making a lot more money on both than I ever did on SB.
Another drawback to Cake if you're a student of the game and intend to use tracking software to track not only your own stats but those of others, is that Cake is THE most strict network about tracking software. You are not allowed to run a HUD, and not allowed to track anybody else's stats. You can track your own stats with approved software like HEM as long as the software complies with their restrictions, but pretty soon you're going to want to run your stats against a specific player and you won't be able to. There are some "hacks" and HH converters to allow you to capture other player's stats but it's a major hassle and not very reliable (the reason Cake allows player name changes every week is to thwart trackers). That was ultimately the final straw for me as I became more enamored with tracking software. They will however allow Hold'em Indicator and Tournament Indicator, which I'd say is the next best thing to a true HUD. My SB affiliate signup was actually to get a free copy of Hold'em Indicator, which was my first poker software.