I own a Bushy M17S. I like it a lot. The iron sights are horrible, though; I have an EOTech holosight strapped to the top of it. Unfortunately its rail is so high above the bore (think 4+ inches between bore and reticle) that a zero at any distance shoots very low at any closer distance.
Good things I've noticed about it:
It's short, but has a long barrel.
Its trigger can be smoothed up a bit with little enough effort.
It's very comfortable to shoot.
It's got that "gee-whiz" cool-factor at the range.
It uses the same mags and ammo that my ARs use.
Bad things I've noticed:
It heats up relatively quickly and stays hot after a couple hundred rounds. (Too hot to comfortably hold the front handguard).
It's finicky about what magazines will seat in it.
It has a higher number of failures-to-feed than either of my ARs.
You can't even begin to think about shooting it left-handed (you could, in an emergency, do this with an AR, and hope you don't get bad things in your face; not so with a bullpup -- it'd be ejecting right into your left cheek).
I'm considering selling it, just because I already have a fixed-stock 20" AR and a telestock 16" AR, so my needs in the 5.56 realm are pretty well covered.
-BP