First impressions: very good at the price, and maybe just very good period
Digital music in our home stereo starts out in FLAC (lots of ripped CDs that sit gathering dust, plus in the last few years lots of downloads purchased in preference at 96/24 or as near as possible, totalling a bit over 7,000 tracks), living on a 2TB hard drive connected to a Cubox i4pro running headless Armbian 5.05, which is basically Ubuntu 16.04.06. The Cubox is connected by a USB to the new Airist R-2R, whose conversion duties were previously handled by a Schiit Bifrost 4490. The rest of the stereo is mostly Linn stuff, so quite decent quality.
First impressions of the R-2R are very positive. It worked with no fuss over USB to the Linux machine, which reports it being able to handle up to 768K in 16 or 32 bit format. There is also a "SPECIAL DSD_U32_BE" format supported but I don't have anything around to try that with at this point in time. No problems playing music, switching bit rates / word lengths, no clicks or pops. The sound quality seems very good. Compared to the Bifrost, my first impressions are that it is a bit less prominent in the bass and makes taller stereo images. Certainly no obvious flaws and lots to enjoy.
I'd especially like to compliment Airist and Drop for getting this right on the Linux end of things. Beyond that, I'm very happy with the unit so far. No regrets.
Shipping to Canada was reasonably quick; arrived in a shade under 3 weeks including customs tomfoolery. Much better than my previous experience with a set of headphones which actually took months.
Would recommend to a friend.