I have tried many over the years, I started with Pokerstars, but then went onto PKR.com, then tried more and found them basically the same, when it came to playing Holdem.
Some offered some great free-rolls, and I made some small bankroll's with a few, but I always seemed to return to Pokerstars.
I have seen a lot of changes, but there is something that always draws me back to my first account, and I stay loyal to Pokerstars, for me Poker is just a Hobby and I don't play to win Money, I just play to win! Money will always be a big part of Poker, but I have played on some game sites that offer nothing more than Play money, and I have had just as much fun playing on them.
The main reason I have not tried to build my P.S. account bigger than it is, is because I started to venture into Live games which I must admit I enjoy a lot more than On-line Poker.
The social interaction was always better, as typed messages on Poker sites can be miss-interpreted and cause friction between players, because coming from different Countries we all have different meanings for some similar words. So you need to be careful when talking On-line.
As for time spent playing Poker, I have never measured it, for me it is a fun pastime I enjoy playing, just the same as playing Chess, Trivial Pursuit, or any other game I enjoy taking part in. It has never been about making Money, just having some Fun!
When the fun Stops, STOP!