Hey Doug,
I too stepped away from the Fantom G and got an M3. Reasons:
1. Great price
2. KARMA - This is a pretty big reason, especially since Korg is now releasing an update for the M3 that will allow users to bake their own GEs (This, IMO is very cool!!) and import them into the M3.
3. Free RADIAS EXB - Analogue capabilities.
4. Korg's software-update strategy, I love the fact that they release so much software/sounds and keep you updated.
I have been playing with the M3 for about 3 days now, only to realize that I would never be happy with **ONLY** the M3 in my arsenal. Big 4 reasons:
1. Sequencer sucks (barely useable, I guess I have been spoilt rotten by my Fantom X), I've heard lots of good music made with the M3 on the forums, so Im thinking it's probably my inability to work with it and produce results.
2. Sounds are good (simple to get a reasonable tone), but the Fantom sound engine is far more advanced, with the dual LFOs (step LFO also) per tone (voice), ring modulator, booster, and the filter and amp envelopes. IMHO one can tweak and achieve better sounds with the Fantom (mine's an X), sounds warmer too.
3. Keys feel toylike and very light to the touch, again spoilt by my Fantom's awesome feel and keys

.
4. I feel that the Fantom (even the X) is much more suited to live play. Patch/effect switching is so easy and for the advanced users there's RPS and the variations.
You know, honestly Im very happy with my purchase of the M3, but having used the Fantom X for so long, I know Im never selling it, it's way too cool, and it totally compliments my M3.
The G is better than the X in lots of ways, wish Roland had done more with it though!! It seemed (and actually still does) like a half baked product, which is why I decided to wait ...
So, make sure you have realized the full potential of your G before you send it back ...

Manish