Played most of my life at Ongame:

$25nl: Donkfest. Easily beatable...play weak/tight and you will get paid off huge. In other words, only build a pot when you get TPTK or better and you are goot most of the time.

$50nl: Nut campers. Very nitty. Lots of fold equity here because the nut campers are thinkers. Agression often takes them off their hand so a nice TAG style was very profitable.

$100nl: Definately looser than $50nl. You'll find a variety of players here...from complete donks to uber loose/agressive. In my estimation, more beatable than $50, however, after 8k hands, I am 1BB/100! Nasty variance...lost 5 straight 80/20's plus one 90/10 for stacks!