AFAIK, the only way to do a full backup is with a custom recovery partition installed, and since the bootloader hasn't been unlocked yet, there's not a way to do that.
I'm not sure what features it offers, but there's an app like Titanium Backup that lets you backup your apps and stuff...just not sure if it backs up the whole ROM so you can flash it back or not.
Assuming HTC didn't change anything or release an OTA update upon its release, if its rooted, someone could try to wireless tether app from the Market and see if it works. Its a free download and works on the N1.