Ooops, missed the ongoing discussion.
If you keep to discussing what a UCS set is and UCS sets in general, then this is ok with me.
If this turns into a discussion on what you'd like, then there's a topic for that.
In my opinion, UCS sets are numbered within the 10000's.
Yes the Death Star is a UCS set.
It's made for Ultimate Collectors.
UCS doesn't neccesarily mean that the set is a huge model like the Millenium Falcon or the ISD.