I used a galileo luna for about 4 years. It's a nice computer, and will get the job done. That said, it's a bit outdated and there are better options out there.
The good : Readable display of a good size. Does what most recreational divers will want. Very easy to use and navigate. It works with subsurface (free third party open source dive software). Price. Since it's an older model, you can get used ones VERY cheap (compared to modern competitors).
The bad: Display is only good for day dives. If you do anything in low vis or at night, it kind of stinks. The backlight is poor and you'll need to shine your light on it, which means reading your computer becomes a 2 hand operation. The compass really sucks, don't bother trying to use it. The infrared PC interface is outdated. it's hard to get irda working on a modern computer. Laptops don't usually ship with built in irda anymore so you'll have to try and get the scubapro usb dongle working. Transmitter is pathetic on battery life. I can't overstate how bad it is. I was only getting about 15 dives on a fresh transmitter battery until I switched battery type to something other than what scubapro ships. There's a detailed post on this forum about the battery swap.
I switched to a shearwater for about a year, this year I replaced the shearwater with a Ratio ix3m. Both of these computers have displays that are FAR better than the scubapro. They're both color, and very bright. They both have compasses that actually work. The shearwater only supports 2 transmitters (which was part of my upgrade decision). The ratio has gps and a host of other features.
Shearwater:
Perdix AI - Shearwater Research
Ratio:
Ratio Dive Computers - Choose a model
If you do go with the galileo luna, look for used ones. They show up all the time for well under $500 with the transmitter.
Bottom line, unless you get into serious technical diving any computer that you know how to operate will work perfectly. Nobody makes dive computers that don't support nitrox, so don't bother considering that a criteria.
A note about air integration: I've used it for years. Except for technical diving, I use it exclusively to monitor my gas pressure. It works very well in both galileo, shearwater, and ratio. Other brands are probably great, too. Combine hoseless AI with an air2 and you can have a regulator with only two hoses!
