Just picked up the latest issue of Imbibe Magazine and they have a one page review of home coffee roasters. At the top of the list is the Behmor 1600. I haven't roasted with this machine myself but I did catch a glimpse of it in action at the SCAA conference back in 2006. Roasts a much bigger batch than the i-Roast that I use and really cuts down on the smoke (which is important for those of us roasting in small apartments!). The only complaint I've heard, which Imbibe mentions in their article is that it can be hard to see the beans as they roast. I would imagine though, that over time you'd be able to get enough information through the small window combined with the smell and the sounds of the roast.
Imbibe has also been generous enough to post a great list of home roasting tips. Check them out here!