The ACR still doesn't have factory SBR barrels, and I will stand by my vow to never buy another carbine that can't be SBR'ed with easily accessible factory parts. As a result, I may get another XCR soon.
I don't know what is taking Bushmaster so long with the barrels.
My copy has the mil spec rails and I have to say it has been almost flawless. (Had a minor problem with bolt hold open) I'm also optimistic now that the 16" 1/7 twist barrels are starting appear as well as the 5.45 conversion. I hope the trend continues........(I really want a 300 BLK barrel and .22lr conversion,,just thinking outloud )
I bought one in 2007. We took it on a training trip to Nevada and ran 1000+ Green tip rounds through as quick as 3 guys could with 3 full mags a pop. We had quite a few light strikes that were easily cleared with the charging handle. We also had quite a few issues with the trigger hanging up and not releasing. I polished the trigger and fixed it from hanging up, but by then I had a bad taste in my mouth, and ended up selling it for what I paid for it. I actually sold it to buy the Masada.