Shadowlands adds new lands to AO but not much more.
Yes, SL does add a completely new lands to explore and missons. They even added the new city of Jobe but beyond that its still the same old Anarchy Online. I didn't really see them fix what they need to fix which was the whole money issue in AO. Besides that SL is a pretty good add on you learn a little more about the back story and you are actally forced to get out of your Yalmaha and walk. Yup thats right in SL you can only walk around from place to place no more speeding thru the land, though there are warp gates but they are only one way.
One tip, make sure you know where your going or where a warp gate takes you before you step into it. It is very easy to get lost in SL and have no idea how to find your way back. Rememeber warp games in SL go ONE WAY so you can't go back the way you came you have to find another way.