Ian, what I like best about the Sporty's handhelds is that when you turn them off they're really off! Almost all of the others just go to sleep and still draw power--only a few milliamps, sure, but enough to run the batteries down in a few weeks. So you can count on them being dead when you need them.
I made two Sporty's ILS landings one day, with another pilot aboard, ready to save us. He wasn't needed--but I didn't wear foggles and was aware of the surroundings all the time, even though I tried to ignore it all. The Sporty's omni thing works reasonably well, although the experience is slightly different from the hardware VORs in a Cessna. I'd probably be able to get un-lost with the Sporty's if GPS goes away, especially if I have a chart handy. (I've actually had GPS go away, over the Chesapeake Bay, so I know the feeling of losing it.)
I haven't tried iFly's synthetic vision seriously for landing yet, but have made a few approaches solo, switching to the outside view on short final. I think it would be better than nothing at all in zero-zero conditions.
Sporty's newest handheld doesn't have the instrument things, but it does have real headset jacks so you don't need to look for the adaptor to use it in flight.