Slow and bulky mail delivery.
Much too slow for my tastes. No speed up or brake functions, so you're travelling at a fixed speed. It makes this game almost impossible, as when a vehicle travelling the same direction as you (only a little bit slower) is in the right lane, you are forced to go to the left, and in the time it takes to pass you've missed two mailboxes and been hit three times.
The size of the 'alien spacecraft' that you control is huge, at least a full lane wide. So there are only two lanes to play in. Taking into account that you have no control over your speed and no fast corners, also with little room to move, things dont look too good.
Suggestion? Make it into at least three lanes, 4 or 5 if you're feeling game, which will force you to make everything just a little smaller, as I feel the game is MUCH too large (size wise, not Mb). Add speed controls and allow the ship you control to move faster. Allow more warning for oncoming traffic (as sometimes it was near impossible to dodge when delivering to the left lane mailbox).
All in all, I wouldn't pass this game. You need to improve it a lot more. Try again when you've jazzed it up a bit.