It's already shaping up to be one hell of a day from Google - first the Galaxy Nexus lands in the Play Store, and now Google Drive is go! Drive.google.com is now up, the app just landed in the Play Store (updated Google Docs), and a pair of videos just hit YouTube details Drive and the SDK.
Once you sign up for the free 5GB of storage space with Drive, it takes you directly into your Google Docs page, where it asks if you want to convert Docs into Drive. Once accepted, you can download the Drive app for your Windows desktop. It will sync all of your docs in .gdocs format. Once double clicked, they will open in your browser.
If you need more than 5GB, no worries - you can get 25GB for $2.49/month, 100GB for $4.99/mo, or even 1TB for $50/mo.
We'll be digging into Drive deeper throughout the day, comparing it to Dropbox, and finding all of the nifty little quirks along the way. Expect a full dive later today.