For a first contest I guess it's not that bad, nothing that can be called an EPIC FAIL.

I think the main problem is more the lifetime of the user in here, some just came here for their school work or for a single problem... and we don't see them after.

How better this would be to have 2nd and 3rd position & prices... time will tell. Better begin the contest somewhere in August and allows 'till November/December for the results. This way you grab the students and the regulars. Post an update/reminder each 1-2 week could help.

my 2 cents