I was at the I Hobbies show for the last few days and saw both the XRB and the Horsefly in flight. The XRB is a much smaller and more precise machine (Hirobo makes beautiful machines). They were selling at the show for $300.00. The Megatech Housefly is approximately the same size as the XRB.
MRC had a coaxial Bell 222, apparently using the XRB mechanics, in their booth. I will probably need one of those when they come out.
I ended up purchasing a Venom Outback Rescue, which is a Horsefly molded in a different color (the yellow tail boom caught my eye). These were flying at the show also and I bought it for just cruising the living room (although it is a little big for that). I have flown it once, and it is almost too stable. It does not like harsh control inputs, but is very easy to manuever in a small space. It required almost no trim, out of the box.
It is ridiculously easy to fly. Very nice when you want to fly, but don't feel like putting a lot of effort into it.
Whichever one you purchase, make sure that you can get parts easily, should the unthinkable happen.