How much of a writeup do you want? I've been running an Ultra Gauge since October in 2 different cars (my 99 4runner and my DD 97 Mazda Protege.)
Right now it's back in the 4runner because I'm getting ready to put the Mazda in the shop. Nice thing about the UG is the "DTE" i.e. Distance To Empty which is my de facto gas gauge (3rd gen 4runners are notorious for having inacurrate gas gauges.)
The MPG readings are spot-on once you get calibrated for distance and MPG.
It's also fine for clearing codes. My Mazda throws a P0170 code all the time, I just reset and drive until it goes off again (from what I've seen on Mazda forums, P0170 is a fuel trim malfunction.)
Unfortunately, Ultra-Gauge's business practices are a little shady. They had proxies post a bunch of "reviews" on car-related message boards that were basically Spam.
The other thing is, their "rebate" is kind of a sham, they give you a convoluted process to go through and then they basically tell you that if you didn't get your rebate, it's because you did something wrong in the application process and they will not allow resubmissions nor will they tell you what you did wrong. So when you factor in the price, just understand that your chance of actually getting the rebate is maybe 2 out of 10.
Other than that, it's a great unit. Worked very well all Winter, looking forward to seeing how it does in Summer. Worked fine in Death Valley and MPG display remained very accurate.
EDIT: Here's a picture. The screen is a little smaller than my GPS (Garmin Nuvi 255w.)
The display is easy to see without being so bright it is distracting. Can also be seen in bright daylight even with sunglasses on.