That G4 17 sounds awesome. Now if only they made them in .40...
Funny about preferences. I prefer the G4 trigger to the G3, and I reload the G4 gun faster than a G3, and about as fast as I have ever reloaded anything.
As far as using G3 bars in G4 guns, I know a few people who do, and it hasn't been a problem yet. Yet. Glock certainly didn't redesign the bar just because.