Hi Brett,
An excellent and very well written and thorough review. I have used an ONAG now for several years and mostly second your observations.
For imagers wanting to go automated and or remote the ONAG can present a few obstacles. The main issue that I see is the lack of a motorized stage. Yes, it's always claimed that with an ONAG you get the whole FOV of the scope but that is only true if you are willing and able to move the stage around. If you are remote (or even just in the house at the computer) this can be an issue unless you have a way to observe just what moving the stage does in real time. I solved this issue by using a Remote Desktop solution on an Ipad. I can carry the Ipad out to the scope and see what stars I can find by going into focus mode with .5 sec images. But, for a truly remote scope this simply won't work. Now admitedly with my ST-i I often didn't need to hunt for a star but recent attempts at imaging the Horsehead required some hunting and movement to the extreme corners of the stage.....and then if you do a meridian flip the star is lost necessitating another move. This can get frustrating. Since I want to use CCDAutopilot on my system I needed to find a way out of this situation. Gaston has previously indicated that there would be a motorized stage coming, but recently he said that will not be the case and he is looking into a different optical way of increasing the available FOV without moving the stage. Being impatient I have gone to an expensive but good solution with an 11 mm diagonal chip in the new ATIK 414EX. This photo shows my ONAG guider FOV vs the full FOV obtained with the G2-8300 imaging camera on my TEC180. The middle FOV is the Trius FOV on the TEC140:
http://www.pbase.com/prejto/image/159103698
Peter