Can't see why there is such a hype about this. Maybe the technology behind it is really cool, but in terms of real use I think it's a dead duck.
Our business needs it's 24/7 high speed web access to the desktop, so there not a huge need for Gears there. Our mobile base uses their PDA's/SmartPhones for calls, and for Exchange Push Email plus a little bit of PIM. (Again from Exchange). Mobile devices will not in the near future be a propper web client - screen and interface is too limited.
Plus taking on Nokia/Symbian which supports Java out of the box, and Microsoft who support the .Net CF out of the box is going to be a huge task.
Don't forget, Google is a great search engine, and Gmail/Maps are quite popular - but hardly killer apps. Trying to hard I think Google.