For me, it's very much:
1. more storage AND additioal expansion capability
2. FAR better guide data
3. a real functional search
Non of those pose any real technical challenge, the really difficult stuff already works pretty well (the whole record and watch, record 2 streams and watch another spun from the drive... this is actually not even vaguely easy to accomplish).
Unfortunately, we are seeing a lot of ad dollars being spent touting remote management & multi-room, 2 functions that are totally worthless to me. So I suspect extra buggy versions that that stuff will come first... after 2-3 years for them to work out the issues, maybe they'll address the easy ones!
Don't get me wrong, while it sucks to be me, I know there are a number of folks who value what I do not as a first priority... so I applaud you guys getting something you may want/need.