Hehe. Actually, if you really enjoyed what you worked on and are satisfied with the results -- i.e., your personal goals for your project were met according to your standards, I don't think there's anything wrong with voting for your own entry, as long as you are honest to yourself that it indeed is your own personal favourite.
I personally wrote Cyberspace Assault as a game I would play and enjoy myself; the features, graphics, music, and gameplay I have built into it is a representation of what I would want a modern shmup to be. It may be a bit far from how others idealize a shmup, but for me, for an application developed in a span of two months, it's nothing less than perfect.
So as a pat in the back to myself for a job well done, I shamelessly vote for my own contest entry.