I've tried a couple of these MIDI to USB interfaces in the past when the technology wasn't the most advanced, but I trust the Roland name and I needed this for my rig, so I gave it a shot.
I was pleasantly surprised at how low the latency truly is, and I didn't twist a single knob or click a single mouse to dial it in. It's frankly unnoticeable, and I've used it on a number of different MIDI instruments and found the performance to be quite consistent between all of them. I've also had no problems whatsoever utilizing it with my DAWs.
The only potential turnoff here is the pricetag, but let's be honest, you're paying for the Mercedes-Benz of simple USB to MIDI Interfaces. If you're considering a cheaper alternative to the UM-One, I would honestly say just suck it up and pay the extra 10-20 bucks for the Roland quality. A quick glance at the competitors and you'll see that the UM-One tends to come out on top, unless you want to pay $100 or more.
Great product. Nothing to complain about. A great solution for linking MIDI instruments with your computer, your DAW, and your rig.