$100 NL is weak. $200 NL is pretty much the same as $100 NL, just double the stakes. The players at $400 NL are a little more tight, but not particularly good in general.

I had a hand earlier today at $400 NL where this guy raised in late position, I tripled his raise with K-K. The flop came J, 7, 7, he checked, I bet about half the pot, he minraised, I went all-in and he called with Q-J and stacked himself. These people don't go away.