I've owned one of these things now for a couple of years. They aren't as accurate as an AR because the trigger is really poor. There's alot of home tinkering you can do to help it a long way, but it will always be worse than an AR trigger. Other than the trigger, there's really no drawbacks to accuracy. Groups run about an inch bigger than an AR, smaller than an AK though.
I wouldn't say it's more reliable either. It's more finiky as to the mag type in it. I've had trouble with last round hold opens with some mags, and not stripping a round out of the mag, and getting rounds loose inside the action (I have no idea how, but I've had fully loaded rounds jiggling around in the receiver). With really good condition USGI mags, I haven't had problems. USGI mags that are used (and work fine in any AR) will sometimes give problems. The gun is far easier to clean and maintain, but I'd still have to say that a high quality AR will have a higher mean time between failure rate, i.e. work better, than the M-17s. All of the failues that I have experienced have been magazine related. Possibly because the whole lower housing is plastic, and maybe it expands or contracts more with heat, or whatever. I dunno, but they've all been mag related one way or another.
There's also alot of other quirks with the gun. Most of them are easy fixes, but they should have been just done right at the factory. Things like no handguard, bogus scope platform, etc. are all things that should have been just designed right from Bushmaster in the first place.
All in all, if I were to grab a gun I needed to work. I would take an AR over the M-17s. It's a very handy gun. The layout takes some getting used to, and you'll either love it or hate it. I like it personally, and I'm still tweaking mine. I expect that sooner or later I'll have the gun where I want it to be in the reliabilty and features department, but it just isn't there quite yet.
I think the M-17s is a good gun, but I still view it as a "work in progress" rather than a fully developed gun that you could stack up against any of the current crop of mil-spec guns (M-16, AUG, FNC, etc).
Ross