I have one of the plastic wheels and its pretty sweet. Haven't gotten one of the Al ones though. The Al one did take less than half an hour so Cory is about right. (Thanks for backing us up on that btw Cory). Like RC said, only one side is pocketed like this.
I actually like the HDPE prototype better. Its cool for low stress applications on class robots plus only takes 5 minutes for RC to make at work. (I'm so mooching off of this kid all the time now lol).