All those who maintain the fixies are too cheap and weak for a motor...
Here's one with over 1k miles and still going strong. No problems so far (aside from a lot of flats)
This Takara seems better built than the thruster, and is holding up much better than I expected. The owner reports no problems with the bike at all.
Even the tires are doing well considering the speeds!
Next time you see one of these for sale at the outlet store for under $75 bucks,go for it!
If more is better, then too much is just enough.
If you can't afford it, build it yourself.