There are several original 356 owners in New England running around with EFI, and two, that I know of, also running crank-fired ignition. All of those were set up by Rainer Cooney at the Meister Restorations in New Hampshire before he spun off his Spyder operation, so 5+ years ago. Those two are 4-Cam Carerra engines that are putting out about the same torque as some of our stouter 2,110's or larger. Plus, they idle dead-smooth (something the original 4-cam engines NEVER did). I also saw a guy from Connecticut at a show last summer with a VW sedan running a CB Performance 2276 and a Gen 4 EFI and he thought it was pretty good - easily programmable with his laptop and from what I gathered, pretty reliable (although.....he was on his second ECU in two years - might be heat related). Other details were tough to get between his poor English and my poor Spanish, but he loved the car.
I guess the success or failure of aftermarket EFI systems depends upon three things: (1) getting a quality, well-tested system to start with that other people have already begun using (so they can do advanced debugging before you get involved), (2) finding the right "tuner" site to help you along with any questions and support as you progress and (3) a certain amount of luck and patience.
The Holly system is intriguing, though, because they have decades of EFI experience in the Street Rod market and have a great rep over there. Like the Holly 450/Autolite 2500 single carb setup for VW's back in the 70's (which was great), I think the Holly EFI for VW's should be just as good.