Gave you 2/5 and 5/10. It strikes me as a first attempt at TD, and as such, it's not a bad one, but it's not great. It does have a good idea in it: I like the option to customize your towers, but there's a bit more work that needs done.
As a first game, this is excellent. As a game overall, it's pretty basic. Some things to consider:
-Graphics. Quality and variety can make or break a game. Even stuff like Retarded Animal Babies, with terrible artwork, is still engaging due to variety and the ease of recognition. Also, special effects like stuff exploding and bullets flying are key. Take a look at Momentum Missile Mayhem, not for mechanics, but for pretty factor. You don't have to be THAT good, but some variety keeps it from looking like psychedelic Othello.
-Sound. Everyone wants to hear stuff blow up, and music keeps it from sounding too much like Pong.
-Variety. I could customize my towers (Again, that's a GREAT idea, you should use it again), but had no way of upgrading them or telling one variety from another. Also, you need more maps. The one map will suffice for a while, but look at the variety in something like GemCraft. Each map is different from the last, but there are enough waves on each map to keep you there for a while...plus some easter eggs that encourage you coming back to the level later.
Overall, this is a stellar example of a first game, just not more than a ho-hum example of a game within this forum. Don't get discouraged, take a look at other games and some of the comments, figure out what you can make better, and do it! I'm looking forward to seeing the custom tower mechanic in the future.