from a development standpoint---the biggest difference I came into was speed (yes it was faster)
and user-defined functions now available (which can be nice---but coming from 6 years of using MS-SQL, it's made me have to think about how to use & design the data layer (not structure, but implementation on the db side))
A minor thing in the overall spec---but the query tool---is light years better, IMO. Bought time you could have a list of your sh!t w/o having to alt-tab back and forth.
Admin---
Clustered Servers are also load balancing now in SQL 2000---so you don't have Server A working for Server B to die---they both respond---and it works especially well if they go off of a shared drive array $$$$.
I could care less about that feature---
That's all I know other then what's been already said