Indeed, as well as the EFD-1000 (when that gets certified as a KI-256 replacement), but how long will these keep running after your alternator fails? It hangs on how big the backup battery is. 30 mins is not enough for real IFR involving long flights.
Well with the G5/600 you have the original backup instruments too. So in theory if you have a vacuum system you could have a vacuum AI as backup, so that in the event of alternator failure, when the aircraft battery goes flat you will still have AI. If you have electric backup AI like the Diamonds do then yes, your backup battery must work for 30 mins.
We have had some decent quotes for a G500 fit and if we go ahead and do it our backup instrumentation will consist of Vacuum AI, external CDI with GS linked to a G430w, Garmin Aera 550 running on aircraft power and battery power. So if the G500 fails we're not much worse off than a conventional instrument aeroplane, and if the alternator goes we can continue to fly for hours if we wanted, certainly long enough to find VFR and / or land. If the engine fails completely then the aeroplane battery should provide power long enough until we hit the deck
Actually the G500 represents very good value for money. The cost of the unit itself if around $14000 and this effectively gives EHSI/AI along with MFD, plus the ability to overlay whatever other data you need to overlay. PLus fitting of course but to upgrade our aeroplane to G500, including completely new panel, GTS800 active traffic system, 430w, EDM930 primary engine instruments etc etc. would take about a month and not be prohibitively expensive. Would certainly be a lot cheaper if you already have IFR approved kit onboard your aeroplane and opted not to have a traffic system or EDM930.
I played with the G500 at AeroExpo thanks to Lees Avionics, and it is a lovely bit of kit, with much the same functionality of the G1000. With the EDM930 the upgrade to our aeroplane would effectively give the same instrumentation as many of the DA42's I rent in the USA.