I Paid Up
This site has done nothing but impress me. Being a programmer myself, I can imagine all of the work that went into making this site. Don't let the ease with which you use the chess board fool you: it was probably really difficult to get it to behave in that way, and in different browsers, no less! Wow. This site is just awesome.
What made me truly want to pay was Tactics Trainer. That is so very very helpful that I wanted more than 10 problems per day. Then I got into Chess Mentor! Oh. My. Goodness. It's just like having a Grand Master right next to you, saying "no, idiot! Don't move there!" at least, it's that way for me. I'd like to think I'm good, but I know I'm not even Master material. At least, not yet. Hopefully with great things like Tactics Trainer and Chess Mentor I'll continue to improve my game.
Thanks Chess.com! You guys just keep rocking.