My two sents worth;
As a pilot working for one of the few night freigh operators who use G100s in Metros, I can tell you I would never use it as a primary means of navigation. I've had it tell me to fly 30deg off track to what the VOR/DME equipment was telling me to do (and yes i crosschecked the Lat/Long). They also regularly drop out for extended periods.
Luckily most places we fly to have DME so you can still use the GPS Arrival plantes. If they dont than the way I see it is if the company doesn't want to spend the money to provide 'safe and legal' equipment than I'll delay the schedule and cost them a lot of extra fuel and engine time required to conduct sector entries and full ndb approaches but I'm not risking my life or licence for anybody.
As for STARS and SID most Non-Jet procedures can be safely flown without a GPS and if they can not tell ATC you are negative RNAV and they will give you radar vectoring which will often shorten you track miles to run.
NF