Staff were friendly and polite, on a personal level they were great to work with. However, they weren't on top of things.
They lost my new license plates (when they gave them to me there was still a post-it note on them saying so) and didn't call me to say so. I had to call several numbers several times to even get back in contact with them to figure out where my plates were.
Also, I registered from out of state and even though Nevada requires you to surrender your old plates, Smog Plus didn't take mine. After talking to a different staff member it turned out this was an error on the part of the technician I worked with on the first visit, but at this point I'd already spent $100 more and made one more trip than I would have if I'd gone to the DMV directly. I had minimal confidence that the registration they'd processed was valid, so I ended up going to the main DMV office to turn in my old plates and confirm things were good to go.
Total, working with Smog Plus doubled the cost of my registration and cost me two more trips than the DMV would have.