I'm still new to this game (april '12), but I've noticed one major thing about your contests.
Most of them (not all) are aiming and helping players that already have rubby-items.
8-hours speeds or Completion upgrades are not found around the block, we don't get them that often.
So the latest Cycle contest for instance requires that we use a 8-hours speed (and up) to enter the contest and win more rubby-items.
I thought I should at least bring it to your attention that the non-rubby players should also have more chances to be rewarded. If they were not playing your game, you would be left with WAY less players, and the rubby-members would have less chalenge with a smaller pop in the game and perhaps end-up with a dying project.
My 2 cents.