I recently purchased the Pro Plus 2 from a local shop and it has been a great computer. I would say to look around... I found mine which included the compass and quick disconnect for a lot less than anywhere else, including online dealers... it was a "Hey, there's a scuba shop we haven't been to! Let's see what they have" deal. Turned out to be a good one so don't rush to get something just because... wait for that deal... it will be there.
As far as function, I only have a few dives on it but I do believe it is very similar because I was also looking at the Mares to buy. You can get the manual online to review it... that was very helpful for me because I wanted to know everything it could do. I was looking specifically for one that handled Nitrox mixtures so that cut out many of the other computers, but I must say, I wasn't too interested in an AI computer (until I got this deal) because of the price differences.
Some of the features... you can set F02 for nitrox dives, adjust your PO2 warning level (1.2 - 1.6), adjust your nitrogen warning level (to be more conservative), manual or water activation, review dives and with $ cable, upload dive profiles to computer and set a warning for low pressure when you first connect it and set a warning pressure and/or time before NDL so you can safely ascend. I set the "on" warning pressure for 2750 and on my last dive it actually went off as I was descending because I has used up a bit on the surface helping with my wife's class. The audible warning was quite sufficient for me. (I didn't have a hood.)
One little quirky thing I noticed... since it has an ascent rate graph... if you quickly grab it and look at it (assuming it is dangling), the warning may go off because the computer thinks you are ascending too fast.
Overall I am very pleased with it. I hope to get many years of use out of it.
Ken