It's heavy, but it does balance well.
The stock trigger is borderline bad. I've felt worse on ARs and 10/22s. Geissele will fix that for you with a Lightning Bow and Super Sabra trigger pack, but bring $$$. Bummer since a lousy AR trigger can be fixed for $50-$100 with an ALG or MBT.
They're gassy when suppressed. The port cover sealing tricks (RTV) and gadgets (gasketed covers) help, but do not eliminate the problem.
Accuracy is not up to par with an AR of similar price. Expect 2-3 MOA with bulk or match ammo and you won't be disappointed.
The rail height is not the same as an AR, so optic mounts designed for the AR won't work perfectly.
Aftermarket is small, but that can be said for anything that's not an AR, 10/22, Glock, or 1911.
"Wow, strat81! That's a lot of downsides. Why would anyone want one of these things?"
GREAT QUESTION!!
It's not an AR. Variety is the spice of life. For the guy that has a baker's dozen ARs in the safe to cover any possible need, the X95 is nice just because it's different. I can eat pizza every day, but sometimes I just want Chinese food (or a kosher hot dog and a knish, as the case may be).
It's short. My X95 with Specwar 556K attached is as long as my unsuppressed 16" ARs. If your gun fantasies have you clearing houses and office buildings but demanding 16" ballistics rather than SBR ballistics, a bullpup is a great choice. Yes, an SBR will get you the same size, but then you have the concussion of an SBR, the tax stamp cost, and the hassle of transporting an SBR across state lines. AR pistols can remedy that, but then you have a brace that may not be as comfortable as a stock and the ATF's on-again-off-again-on-again bullshit with shouldering a pistol brace.
They're fun rifles, but I wouldn't recommend one as someone's first or second 5.56 semi-auto rifle, nor would I recommend one to someone that's a bit price sensitive.