jvfish,
I bought an '03 KX 250 from them last fall. I was a little skittish at first about dealing with a company located in BC, Canada (I live in PA), but the deal went smoothly and I ended up with a $5800 bike for $4100 including delivery.
They used to deal under the name of Goodfellow Racing on **** as well. I basically waited until they had the bike I wanted listed on ****, and I bought it from there so I would be somewhat protected under ****'s insurance if the deal went south. But like I said, it worked out perfectly for me, and I know others have had similar experiences with them (just do a search for Motorcycle Brokers).
My understanding of it is that Zach Graham, the owner, is able to offer excellent deals on bikes due in part to both low overhead (all internet sales, no showroom, etc), a more favorable import tax to Canada vs. the US, and also the favorable exchange rate between US and Canadian dollars. As such, I believe he only will sell bikes at the advertised prices to US buyers.
The only problem that I remember anyone expressing when I did my research was that it was difficult to get the bike titled in their state without a title from Motorcycle Brokers. This wasn't a problem for me in PA, but in some states that require bikes to be registered (CA maybe?) it could turn out to be a hassle. Hope this helps, and like I said try a search and you should find a bunch of other responses.