Having done this (switched from a 3 screen GDU 37X based system to a single GDU 475 + 796 with GDL39 3D), I would do it again.
At first I was all hung up on the fact that the GDU 370 PFD2 on the Co-Pilot side was not compatible with the new GDU 465. I even thought about cutting a new panel so I could fit 2 GDU 46X's in but found that next to impossible after trying to make the two screens fit along with the radio stack and keeping the independent stand alone backup D6 in the panel. This was also more pain and agony than I wanted to go thru!
I also realized that putting a 2nd GDU 46X configured as a MFD on the Co-pilot side really did not provide the same functionality of the PFD1/MFD/PFD2 combo that I already had. What I mean is: What good does it do to have a second GDU 46X MFD way over on the Co-Pilot side? Sure you could configure both screens as PFD's but then you lose the awesome functionality of a dedicated MFD screen. A MFD over on the co-pilot side would not be very useful in my opinion.
So that left me thinking about what my options were and what would cost me the least and leverage what I already had. I really analyzed what I use that existing PFD2 for and 98% of the time it was used as a full screen traffic display and the rest of the time was on the rare occasion that I had a passenger that needed a flight display to look at.
Then Steve announced that they had brought support for the new GDL39 3D to the 79X which I happened to have already. This made the choice to upgrade easier since I was able to replace the majority of the functionality of the existing PFD2 with the 796/GDL39 3D combo. The only meaningful thing I lost was reversionary redundancy with going from 3 screens to 1. (Keep in mind that I have a totally independent stand along backup D6)
As for the work involved in making the switch, depending on how your original system was wired, you may need to make some changes to where the serial and audio devices are connected. Also an adapter plate of some sort will most likely need to be fabricated to adapt the new larger screen to the 2 existing holes. The units are really close to the same dimension vertically but horizontally 2 GDU 37X screens are a bit wider than a GDU 47X.
So far this is what I have noticed that I have gained over the original system:
Big nice full screen PFD with much larger field of view for SVX! One GDU 46X has 215,040 more pixels than 2 GDU 37X's.
Super good performance on screen refresh, map and chart redrawing, panning and zooming etc. Major boost in processing power.
Much beefier design. Better knobs! (same knobs as on the GTN series)
Dedicated knobs for stuff that is more natural to change with a twisting motion like HDG/ALT bug's and BARO.
Obviously the touch screen features which appear to be well done and designed from the ground up as an easy to use interface.
Awesome new format sectional charts are standard
Inset overlays for the map, flight plan and external video if you have it right on the full screen flight display.
Full GPS flight plan including holds and procedure turns are overlaid on all maps, charts and sectionals.
Traffic and weather are also shown on the inset overlay map.
Touch tuning of the Xponder, touch control of the AFCS, touch tuning of the new Garmin radios.
Touch setup of the EMS parameters which is a huge time saver over twisting knobs.
I am sure I am leaving some out but I have only flown three short flights so far with the unit. One thing that amazes me is how even though the GDU 46X appears to be designed from the ground up as a brand new hardware and software foundation, aside from the obvious touch user interface, it is still a G3X system and anyone familiar with the GDU 37X based system will be very familiar with it out of the box. TeamX really did a good job porting all the great things about the original G3X to the Touch. This is a major accomplishment since this is more than just slapping a touchscreen on top of an existing design.
