Hey there, my partner and I both have the Mares Quad Air + transmitter, too. Had it a little longer than you. My general experience with it has been fine/positive, although I don't have a lot to compare it against. The large screen is easy to read and navigating through the screens has become pretty natural. I keep meaning to take advantage of the software to keep a digital dive log, but I haven't done it---mainly because I'm lazy and also because I like the tactile feeling of keeping a written log.
The two units have held up pretty well, although the first time we replaced the batteries (in Mexico, probably unrelated), the date setting seem to get permanently screwed up. We took them to our LDS and Mares sent us back totally new computers and transmitters---which was great customer service, but it was also like, jeez, you guys can't fix this overall minor issue? My partner also had a recent weird glitch where she definitely had over 1000 psi in her tank when she surfaced, but the transmitter was blinking red (which is supposed to mean you're below the 750 psi tank reserve), and the computer registered no data at all for the ending psi. Did some troubleshooting with the LDS with ultimately no clear answers as to what happened. But so far, it hasn't happened again (and we dive with back up computers and SPGs), so....?
Overall verdict: I don't regret buying it, but I would probably opt for of one of the other currently top-rated AI models if I had to buy another computer today.