Ubuntu 15.10 here, freshly upgraded. I used to have a bug that I hoped would have been fixed with this release, but it's still here, and it's annoying as hell for me as I work a lot with small TXT files.
The Preview / quickview function in Nautilus, triggered with Space key, doesn't work anymore for TXT file, it keeps "loading" and never shows the actual content of the file. The function seems a little buggy for other files, sometimes it hangs a bit before showing it, but it works (tested with AVI, PDF, PNG, JPG, DOC).
I noticed it doesn't work with DOCX neither (but the preview works with DOC), and Nautilus used to show the actual content of the file instead of the icon, now it's just the generic "W" icon...
Changing the Icon pack with Unity Tweak Tool don't seem to fix anything...
I think the bug is related with gloobus-preview utility, but I'm not even sure it's still running on 15.10? (See http://www.webupd8.org/2015/01/quick-file-previewer-gloobus-preview.html)
I installed Gloobus-preview utility, which has the same functionnality, and it does the same weird stuff, that is, not displaying Text files, but working ok for other file formats.
– greguti Dec 14 '15 at 19:40