Hi fyh,
Both my husband and I use the Mares Puck computer. It's my first computer, so my only other experience is with a rental that I didn't really become very familiar with, so I can't really compare it to others. Still, I'm happy to share my impressions of the Puck.
What I like about it: conservative algorithym, ascent rate monitor, big and easy to read numbers, No deco time and depth very prominently displayed, can be used for Nitrox if I decide to go that route in the future, gives temperature (I love knowing this), one big easy to use button, different settings for use with fresh or salt water, price.
What I'm not as thrilled about: The manual is so-so. Still, it only took me about 30-40 minutes of playing around with the manual and computer before I felt comfortable navigating between screens. Also, the wrist mounted puck is a little bulky compared to the Suunto I rented before, but that model was a lot more expensive. Granted, I am very thin and have TINY wrists, but over my wetsuit it sits comfortably. It fits just fine on my husband's larger wrist.
We both like the Puck a lot--I'd buy this computer again if I had to replace it.