Certainly not the worst debut I've heard on here. I quite like the quiet part of the intro, but as others have said, the looping of the main riff is a bit repetitive - maybe cut a couple of bars? There is also a noticable difference in the sound of the two versions you have used, but a bit of careful EQ'ing might be able to remedy that, and make the transitions a bit less obvious. I also noticed that the pitch seems to change slightly at 4:23. Don't like the ending, sorry. It's too much messing about, in my opinion.
TYMD probably isn't one of the easier tracks to play with, as there isn't that much additional material to work with. Repeating a riff over and over isn't really all that interesting, but you have some good ideas, this wasn't a bad effort at all, and I look forward to hearing some more of your mixes. :)
Remember to deliver with the speed of light
A little bit of love and joy