I love Dropbox and Google Drive would have a hard time getting me to switch. Dropbox seems to "get it" when it comes to simple, easy to use file synchronization.
The one area that GDrive might wiggle into is making it even easier to use Google Docs. I really like GDocs but I don't use them very much because its just not convenient to do so with local files. However, if I can "upload" a file to a directory on my machine and have it available in GDocs, that might turn the tide.
NOTE: One thing that Dropbox doesn't do well is file segregation; some files I want only on some machines. For example, I want me personal finance stuff on all my machines at home but not my work laptop. Or I want large ZIP archives on everything but my phone. Maybe GDrive will tackle this problem...
One thing that Dropbox doesn't do well is file segregation
Dropbox does do that. In the preferences, each folder has a checkbox for "Sync this folder to this computer"; uncheck it and the folder won't be on that device. It's marginally clunky to set up since you have to do it for each folder on each device - it doesn't have a higher level abstraction like "no large zip archives" - but the functionality is there.
The trick here is that Dropbox has introduced this feature pretty late and only if you run the installer now (on a new machine perhaps) you'll notice the feature is there because the installer will ask you if you want to sync everything or selectively.
If I remember correctly, the older clients don't update to new versions automatically (or at least this was the case a year ago) and you will need to download a new client to make this feature available.
We could see much better syncing for Android devices for one. It would be nice if you could have the same kind of syncing that Chrome has when you log-in with your Google account, but for Android. So you could sync everything from SMS messages, photos, videos, documents, and even apps. When you buy a new Android phone, you would just login with the Gmail account, and everything would be there.
I really hope that's where they are going with this, and it's not just a rebranded Google Docs that allows you to store different file types.
They seem to be moving in that direction. The Google+ application on my phone offers instant uploading of pictures and videos to google+ already which I find rather useful.
Your second paragraph is a really good point - if dropping a file into my GDrive-watched-folder makes it instantly accessible in Google Docs, and saving a file in Google Docs makes it appear in my local folder, then that sounds like a compelling piece of UX.
The one area that GDrive might wiggle into is making it even easier to use Google Docs. I really like GDocs but I don't use them very much because its just not convenient to do so with local files. However, if I can "upload" a file to a directory on my machine and have it available in GDocs, that might turn the tide.
NOTE: One thing that Dropbox doesn't do well is file segregation; some files I want only on some machines. For example, I want me personal finance stuff on all my machines at home but not my work laptop. Or I want large ZIP archives on everything but my phone. Maybe GDrive will tackle this problem...