I have an Aeris 300G and really like it. It is not wrist mountable, but I clip in the middle of the BC so I can just look down and see all the info.
I really like the Analog SPG since I don't trust digitals when it comes to air remaining (although they are probably just as good) and the SPG "shares" some its functions with the computer. For example, if you hit 500 psi, a warning tone sounds. Also the backlight for the computer works for the SPG.
The Aeris 300G came recommended by my dive instructor (he uses one) and it is my first computer. The layout it great and it' s easy to read. One issue I have with using it is the beeps that go off when my ascent rate is too high. I can't tell if it's me who's beeping or my dive buddy (also using a 300G) and I don't know if it's beeping because my rate is too high or something else since other warnings sound the same. This gripe will probably be eliminated with more use by me.
The other issue I have with the 300G is that it is not water activated. You have to manually turn it on and start a dive within 2 hours of when you activate it. Once you start a dive, you can't activate it, since it takes the altitude reading pressure once it is activated. You may be at 50ft but the computer will say 0 or error or something like that. So far, I have always remembered to turn it on before the dive (knock on wood), but I would prefer water activation.
The instruction manual is pretty easy to read as well and it comes with a quick reference card.
Overall, I give the 300G a thumbs up. I wish it was water activated though. I know one day I will forget to turn it on and then won't be able to use it.
Take a look at their website
www.diveaeris.com
Hope this helped.
- JG