I'm on the border of deciding whether to pay $99 or not

I've been on this site for a while now, and I can say that I enjoy it's features. I want to upgrade, but I'm not sure if it's worth it.

The main reason to go diamond is for ChessMentor (IMHO).  Try these free courses and see if you like the format:

http://www.chess.com/blog/webmaster/free-chess-mentor-courses

Do they plan to fix lag and connection problems? A client perhaps, where you could play from the actual desktop, not needing to load all unneccessary elements of a webpage at all times? If so, I'd consider it, but with these problems, it's not worth it.

If I had to do it all over again, I wouldn't.

I think it's the best $100 I spend all year, but then I really use the features.

I had diamond membership and it was nice; not going to pay the full $100 again right away though. Best part are Daniel Rensch's Live Sessions videos- entertaining and instructive.

Like anything else, you get what you pay for. If you are going to use the features, it may be worth it.

Looks like OP decided against it.  Good choice.

I got the platinum for chess mentor, and I trained for hours last month but this morning I got a screen that told me I had my maximum lessons for today, I feel cheated and I am not sure I think platinum is worth the money now either.