It really depends upon what you're looking for in a poker site
. Most of these responses seem to be in regards to playing the freerolls so I can't offer much advice on that topic (as far as the reg. freerolls go) but do know that Fulltilt has alot of private forum freerolls running on it (Stars had some.. but now??...). Cardschat holds a good freeroll on Fulltilt twice per week which would be more than enough reason in my opinion to sign up to Fulltilt, pronto.
I normally play the $6-$11 sngs, $26+ mtts, 25NL ring game &/or 6-max, and some priv tourneys & freerolls occassionally.
Out of curiousity yesterday, I was going thru my freeroll cashes on Fulltilt (having played a bunch of them early in '08 but not too many after July) and decided to add up the total I've cashed in them.
$238.32 .... not too bad. Maybe even more reason to get signed up on Fulltilt??
I play on a handful of sites, playing different games on each but I'd say that 90% of my time is now on Fulltilt and has been for awhile.
Pokerstars I find to be pretty lame,... the micro buy-in sngs are painful to play as are their large-field, micro buyin mtts. 10 & 25NL cash tables there are very easy to beat so this is what I will usually play on there. Of course Cardschat has some excellent 'cash-added' micro buyin tournaments running again now each Sunday on Stars also. These are great!!
I haven't played much on Carbon but have heard from a few sources that the micro buyin ($5 & under) sngs are easy to beat and are fun to play. I've only played private tourneys on that site and really dislike the structure of the tournaments (blinds get really huge before the bubble bursts and game becomes a push/fold game very early,... with stack sizes in relation to blind sizes leaving avg. stack on about '5M' even before bubble bursts). BUT.. as I mentioned, I've heard the micro sngs on there are very good.
I play on Doyles as well but not nearly as much as in the past. That site has dropped all kinds of stuff it used to have on there but is getting ready to switch over to a new network so I'm assuming that this is why (ie. no more priv. tourneys, no more 'raked-hand' required $500 freerolls, and most of the tables have switched over to 'euros'). I still go there occassionally to play cash tables.... just seems like I run pretty good there on them and use it to practise my cash-game play (I built my Doyles account up strictly from freerolls at first, cashing in one they had on NewYearsDay Jan1/08 for some pennies and then built it up from there... over $300 now, but would be more but I transfer to friends there occassionally).
Not sure if this helps you out at all. To sum it all up.... Fulltilt all the way!!!