change of UI
A change of interface will highly generate a lot of interest . Microsoft Ribbon interface is a perfect candidate for the desktop app. An alternative UI can be adobe bridge. Microsoft Ribbon is the best because of windows 8 explorer and also ms office app and these are highly used apps. both basic and advanced people can still use the app as a replacement for browsing their files whiles tagging.
I like the UI very much, but i like ribbon style when done right and flexible very much too.
Maybe this is something that can be done if and when the UI is anyway worked over for the next big version. But i dont think it is a major issue, better would be to optimize the current UI:
Like with some of my and other RQSTs:
-Right click context menu on files and dirs
-One click files opening option
-Direct Editing when opened for document files
Richard Sugg commented
Current UI is great. I suppose there are many of us who don't use windows at all, so a Ribbon interface would make us physically sick.
Tag Spaces is simple to operate and the UI should refect that. Some colour to the UI wouldn't do any harm though, it's not very interesting to look at as it is.
I certainly don't think adding a different UI will generate much, if any extra interest, UI is a subjective issue and there are many people who dislike MS Ribbon as an example.
Claudius Ellsel commented
I like the current UI as well.