Whilst I would normally embrace anything Google, I've got to say that it's lacking in some areas compared to Dropbox (the only other similar service I use and can therefore compare).
The biggest drawback for me with my tiny download speeds is not being able to see transfer rates or limit them. 5GB, whilst not bad for free, lacks to Dropbox too (although the paid options are cheaper; I'm a cheap-skate).
Even the fact the the systray icon does next to nothing to show that it's syncing is more annoying than a full on flashing icon.
Can't really comment on the app too much as it downloads, but won't install. In fact, trying to get back to the market again causes the market to close =/
I'm still gonna use it for a while, but unless they start looking at competitors and saying "these are the things we should be doing", I can see this becoming as popular as Wave