I am a big fan of the Gekko. I purchased my Gekko when I first started diving 3-1/2 years ago. I dive fairly actively. I've never really had a need to upgrade. The Gekko will Nitrox dive with you. It will not tri-mix dive. I have found my Gekko to be very dependable.
Also, when comparing computers, be sure to thoroughly investigate the user button interface and menu interface. I was on a Caribbean boat last year and the group wanted to do a nitrox dive. I picked my gekko up and with a couple of very intuitive button pushes, I had set my Gekko up for 32% O2.
There was a small group of divers on the boat diving a different brand of computer (I don't remember which brand). They had been bragging all week about how great their computers were and how easy they were to use. When the nitrox dive was announced, I had my computer set and was enjoying a cold drink and watermelon in about 10 seconds. Of this group of four with the other brand, three of them had their computer manuals out reading through the Settings section. I will bet it took them somewhere between 10 and 15 minutes to figure out to set their computers up for nitrox. As I recall, it involved some bizarre ritual of hold this button for two seconds. Hold that button for three seconds. Flip through six menus. Hold this button for another two seconds . . . . . . . . You get the idea.
I was a little bit bummed that the Gekko would not download dive logs; but now I see that problem has been hacked!
JR