Didn't look up the above sites, but as far as I know it is legal to play poker online. The only thing illegal is for online poker sites to accept money from us residents. So, the problem is getting your money in.
I play at PokerStars and Full Tilt Poker and I haven't experienced any kinds of problems so far.
The only issue that I got was when I was adding funds to my account. I used my credit card and my bank denied it. They put restrictions that prevent purchases at online gaming sites which is an increasingly common problems for player in the US. Lots of alternatives though so it's really not that big of a deal.