In RC1 and RC2 in the Administration Control Panel,

When uploading from your machine, upon clicking Submit, the successful message is displayed, but no avatar is uploaded and no entry is made in the database. Additionally, dimensions and filesize are not checked.
When uploading from remote url, upon clicking Submit, the successful message is displayed, but no avatar is uploaded and no entry is made in the database. Dimensions and filesize ARE checked.

Uploaded avatars work fine in the UCP.