I think a lot depends on your intended missions. If you are flying IFR a lot and on long flights, I find the altitude hold a welcomed relief and a great assist especially if I am being re-routed with a complex route. It allows me to use it as a CRM tool so I can concentrate on setting up the rest of the panel to accept the new routing. Could I do it without altitude, yep, did it for years with a basic wing leveler that worked half of the time.
As for the ILS vertical guidance, as KSM stated above it, for our class of plane it may be a luxury. That said, I have that luxury, including auto trim and I have flown a number of approaches with it engaged. When you are flying single pilot IFR to a low approach, it is just another tool in the box that you can use.
I can do everything my autopilot can do (and more, I can think) but will use my AP to its fullest. And for the purist out there, what I said above may be sacrilegious; but I didn't buy it for "in case of emergency, Push HDG & ALT". I bought it to be part of my CRM.
APs are not cheap, even the upgrades. If you find you want/need the extra features, factor that into the FMV of the plane you are considering.