Derivitive But Fun
I like it. Sure, it's Desktop Tower Defense with different sprites, but you're upfront about your influence, which counts for a lot. The addition of multiple playing fields is a GREAT addition, forcing you to adapt from one stale maze to using terrain. However, now that you've managed to improve DTD, it would be great to add to it. How about an update\sequel with new features? A few quick ideas off the top of my head:
-Cheap walls to build a quick maze without having masses of vulcans dropping your FPS would be a great idea.
-Fire pits or mines that you can drop in your maze for the creeps to walk over.
-Global upgrades for your towers (range, damage, ROF, etc.). Possibly requiring an oversized building that does not attack forcing you to plan it into your maze, especially so in higher levels.
-Synergy towers that can augment each other if placed within a certain range of each other (think Prism towers from RA2).
-Bringing back the DTD level crawler, or announcing ahead of time "Next wave will be a (x) wave".
Go on from here. You've proven that you can recreate DTD and add new features to it. Prove the people that say you're just ripping someone off wrong. If you're up to making it, I'm definitely up to playing it :)