I'm perfectly happy with my Quest.
Postcodes aren't really an issue for me as I use the bike for recreation rather than every day transport. What I'm saying is that trips are planned on the PC and if postcode location is required I can use AutoRoute to either find the location or create the whole route in AR and then convert to GDB using
GPSBabel. The address search logic on the unit is a little strange but OK once you get used to it.
The screen is a touch on the small side but I only rely on it for a quick glance of the road/junction ahead occasionally, the audio instructions are the main output whilst I'm riding.
One problem with the Quest is the limited amount of memory, the UK model has 256MB of which 243MB can be used for uploaded mapping. This will fit the whole of the UK but if you plan to use the unit for extended European touring then, due to the tile size of City Navigator, your range will be limited.
See here for an explanation.
The earlier mapping for the Quest, City Select, had smaller map tiles which used far less memory on extended routes. MetroGuide Europe uses these smaller map tiles but, out of the shrink wrap, isn't routable on the Quest, only in Mapsource. However, using a free utility called
MetroWizzz it's possible to create the index that gets uploaded with the mapping to make it routable. The only downside is that roundabouts are treated as normal junctions by the audio instructions, you get "turn right" rather than "take 3rd exit", a small price to pay. MetroGuide Europe can be purchased on eBay for not a lot of £ (currently on version v8 but v9 has been announced and is due out v. soon)