I've noticed that too about 50 NL games, on different sites. A lot of the players won't play anything less than premium, and it's very tough to play any kinds of hands with implied odds other than pocket pairs due to lack of action.

So if you have a session without anything better than AA/KK, its probably going to be a boring/losing one.

I'm not in the range for 100 NL yet, but it probably is much better than 50. I actually prefer 25 NL anyways.