I use the UM2 for connecting to my iMac for recording and controlling both Guitar and Mic inputs.
It is basically just plug and play. In Logic Pro X you are presented with two Inputs (1 & 2), 1 goes for Mic/Line 1 and 2 for Instrument fx. Guitar). Both inputs gain can easily be adjusted by the two knobs on the UM2. Sound quality from inputs are really good. Using the UM2 as sound output on the iMac is quiet nice, as the iMac has no other output than headphones or Bluetooth, where BT has a delay, using the UM2 there basically isn't any delay. My speakers have analogue RCA input, which works well with the UM2. Output sound quality is good, which means that the UM2 has a good D/A converter build in. Monitoring is also nice, it can be used easily to monitor the inputs directly throug headphones. I'm using both acoustic Western Guitar and Electric Guitar with the UM2, and the result for clean sound is awesome.
Pros/Cons: Build quality is actually quiet good, though the knobs would have gotten a better "touch" if there were made en metal instead of plastic, but that is just a cosmetic feel. It is very easy to use and adjust. It's good it has signal LED's to show when it can register signal, and it also has a clip LED so you easy can adjust input gain to a normalized level.
I am new to using instruments through the computer, but this made it really easy to get started.