I'm not sure what Au may or may not have been responsible for, but the Android tablet is the first time I've been wow'd by a Google UX. I'd be more interested in seeing Matias Duarte's picks.
I think you meant to say Google UI. There are a lot of instances where people think Google's UI is not polished. UX is more than just the UI you see on Android tablet. Some notable UX achievements of Google:
- Search
- Google Analytics
- Gmail, gmaps, calenders, spreadsheets, etc
- Groups
UX failures: (and yet had pretty decent UI's)
- Buzz
- Wave
Sidenote - TIL about bagcheck.com, looks pretty cool.
- GMail -- more for the rich use of javascript that a stunning UI. Effective, simple, and performant.
- The main website -- simple, loads quickly, etc.
- Android (Froyo and beyond) -- there are elements I really wish Apple would adopt - widgets, unobtrusive notification system, etc.
Beyond those, I really haven't seen a UI/UX example from google worth being wow'd about.