The first impression is very good, mostly because nothing has been revolutionized (in appearance), so I felt immediately comfortable with the new version.
For now, the only thing that I noticed that is slightly different is the post form, that IMHO now is better and clearer:
- the interface elements has been reorganized to make it sempler
- heavy use of DHMTL let the user customize the UI following its needs
- the visual editor has everything is needed
- the changes to the UI are remembered (nice!)
- the preview now shows the post as it will appear to the reades, complete with all theme elements
- last but not the least, the file upload is there
The only thedious work was editing the theme files, but this is inevitable.
So, in conclusion, this is a very good work: kudos to WP team!
Edit: I forgot… er… localization (for example, see WP in Italian.) To my knowledge, localization doesn’t not work automatically and you have to set language explicitly in config file.