I am installing a Garmin GFC 500/P and choosing (for now) not to upgrade my GPS box, so I'm sticking with the 430W that works perfectly fine and I know the switchology well. I've read that the VNAV mode for the GFC500 won't interface with the older 430 and I'm trying to figure out what exactly I'll lose there. I understand it won't fly LNAV profile to meet altitude at a certain fix, but not sure how that will limit approach capabilities of the new A/P. I am also interested to hear of any other limitations pilots have experienced with this configuration. Does anyone have this configuration? Any commentary is welcomed . . .