GRT + Garmin + ??? Interfaces
The Widget videos were indeed very nice, and I'd not seen those before. Hats off to him for making the effort to produce them.
I have a Sport SX, with a Garmin 430W, driving a TruTrak (now B-K) AP--the xCruze 100 (upgraded from a DigiFlight II). Consistent with comments of others, GRT has done a great design job to ensure the boxes from various manufacturers play together well. The gap is that there are a number of things that need to be done at proper times, e.g. while the various boxes interact well, the overall integration is a bit complex than more fully integrated designs. It's also not practical for manual writers to anticipate all of the potential combinations. Because of that, I found it helpful to create a step-by-step "bullet point" procedures document. That took a few iterations, and a few phone calls to GRT (thanks, Jeff!).
With my combination, the specific procedures are a bit different depending on whether the approach is an ILS or GPS/LPV, whether you fly the full approach (possibly including a PT or HILPT) or get vectors, etc... Also depending on whether it's an ILS or GPS approach, the missed approach procedures are slightly different as well. For example, if the Lateral AP is in GNAV, it won't couple to a GS. If in ENAV, it will fly the GS, but won't fly PTs, holds, etc... that reside in the Garmin d-base. As another example, if there are mandatory step-down fixes prior to GS intercept (think mountains), you need wait to press "EXECUTE" until you've passed that last step-down fix.
In the end, the boxes will fly both the lateral and vertical aspects of an approach like the A/C is on rails, but there are just enough nuances between various types of approaches that I find the bullet point document to be helpful. Of course it's important to have those procedures ingrained rather than trying to follow a "do list", but when I'm approaching my destination and am expecting a specific approach, I'll often pull that document out and do a quick review--both of the setup and also the missed approach buttonology.