I don't know how good it is for the single pilot IFR scenario. Obviously every bit of situational awareness helps but if flying say an ILS, will you fly it on the HSI, or perhaps the FD, or by looking at the FliteDeck moving map?
I think it is easier to use than you might imagine.
Flying the ILS segement of an approach clearly you would ignore the PDF and fly the ILS using the command bars on the PDF and or would monitor the command bars if flying a coupled approach.
For non precision approaches I suspect most people would be flying coupled approaches using the GPS for primary guidance these days. I think the combination of the autopilot in and the plate on the PDF provides a superb means of monitoring your progress through the procedure including the descent segements where the plate provides the visual clues for intiating the step downs and adjusting the VS rate to capture the correct gradient.
Take the autopilot out or use just the heading bug and flying a radial such as the cross country approach into Lydd and it becomes a delight with the plate running on the MDF.
I think it is a great bit of kit for the "serious" IFR commuter, not that I make any claim to be such. Of course, and as always, staying ahead of the aircraft is the key. Personally I think both Avidyne and Garmin could have produced a more slick user interface. As it is I think you do well to ensure the correct plates are pulled up well before you start the procedure and both the MDF and PDF are correctly configured. I guess there are no surprises there but you would have to be pretty comfortable with the systems to work the PDF and MDF on the fly single pilot in a procedure with which you were not familiar.