Regarding the above website:
A) Have you used it before?
B) If so, is it worth my time?
C) If so, are there any similar websites that you know?
A) Yes, I've used it.
B) No. It sucks. It's great for beginners because there are many youtube videos and wikis with the answers to most of the problems, but if you're an advanced hacker, that site would totally not be worth your time. I don't think the forums work well; there's no way for you to communicate with your fellow members.
C) HBH (hellboundhackers.org) OK site, but it's going up for auction in the meantime.
EG (enigmagroup.org) The best I've been on so far... I'd totally recommend this site.