-Good User Manuals, FAQs and perhaps some Video tutorials. (I RT*M first)
-Responsive tech support and customer service.
-Stable and reliable connection to wi-fi or 3g (initially a glitch with the Nexus One, which tried to jump back and forth between Edge/3g/wifi, solved after the froyo update)
-Seamless integration with existing Google services in the custom apps. (gmail/maps/calendar/voice/checkout/etc.)
-USB Host drivers for most USB peripherals (hubs, ext. storage, HIDs, speakers, etc. Microphones, webcams etc. would be nice too)
-easy bluetooth setup (including for VTech phones, printers, etc.)
-a nice paint/draw app (photo & video editing would be a plus)
and last but not least (actually probably first of all):
-Pixel Qi screen goodness....