Sync is a misleading term here. What the new Android Dropbox app added is an Automatic photo/video uploader, to a pre-defined folder on the server side. One way.
I should add that Dropsync is also capable of Instant uploading, and not only photos/videos. Any new/modified files in your designated local folders in your phone/tablet.
Dropbox really had to play catchup on this one: lots of competitors offered this (Sugarsync, Box, etc), and lots of addon tools for Android were popping up with this functionality.
I wonder how Dropbox is going to handle the tradeoff of syncing lots of data (to/from a space limited device) and cellular data limits. I sure hope there is an option to only transfer over Wifi.
In testing DropBox's new client out:
1) There is no way to start the import wizard via menu dropdown.
2) There is no way to specify an alternate folder(s).
There should definitely be a an option "Sync Photos over Wifi Only" and it should probably be the default.
Google+ let's you choose, so I love snapping shots and then having them show up there whenever I get home. Even with my unlimited data, I'd still prefer wifi.
If you want true two-way sync for Android, try Dropsync (https://market.android.com/details?id=com.ttxapps.dropsync). Another app called FolderSync also seems quite good.
Full disclosure: I am the author of Dropsync