Interesting find, dray. He is listing the clearanced motor as a 350W motor, rather than the 500W motor currently on offer. Perhaps that is an earlier generation? 350W would probably be underwhelming, compared to the 25mph estimate listed on the site.
A 500W motor should be able to get a 200lb rider to about 18-20mph. There are a few real-world users posting around on this site, they all seem to have the current generation 500W motor, and are providing acceptable to favorable reviews. If you go over to instructables.com you can find an electric bike conversion by watermelon using the current kit. He seems to like his kit just fine.
I don't have any experience with the kit as yet, as I'm still trying to decide whether to get one myself.
-Mike