How usable is the Android browser on "average" web sites?
I'd say it's highly usable, I have for the most part stopped using a PC outside of work, my phone is now my primary browsing device.

On the rare occasion a site doesn't render properly, or a particular video is not available on mobile (this happens a lot on YouTube) you can email a link to the website to yourself to check when you are on computer in 3-4 clicks.