First of all it looks like the original link xbox.com/rewards returns you to an error page. If you want to access the rewards system try This Link, it seems to work for me.
Since there were so many problems with the sign up process, and the site performance Microsoft has decided to extend the time in which you have to obtain the required amount of points by a few days, and apparently have increased the number of prizes they will be giving out - sounds great to me!
They have added a gamercard system that you can use to promote / gloat your rewards status - I am guessing the bottom area is to list the rewards you have obtained or something like that.
I currently need 385 points to obtain the level 3 challenge! I don’t have any games on hand thats going to make getting there extremely easy - but I think I might be able to complete the challenge today. I actually have NBA Live 06, which is known for gaining gamerscore without much (if any) work, but the copy i got from the rental wont even load on my xbox - and with the current weather exchanging it is out of the question.
Also for the record, if you click the finish button and you are not in fact finished it will simply let you know that like so:
