The guys who capable of improving modern Linux desktop are using Mac. So we are losing momentum in Linux desktop targeted software or facility.
They are developing in Mac but targeting server software or devops tools. So pretty modern, hot and bleeding edge things are happening in there but not desktop area.
GNOME - Always doing some experiment. No application. Just changing shell. No reliable usability. Call me when they are done. One good thing about GNOME is they care about beauty and elegance.
KDE - They just don't care about beauty of ... anything. But their applications are freaking featureful, reliable and developed by people who actually using it. I can feel they are dogfooding. I saw KF5 screenshots. They still don't care about beauty.
ElementaryOS(Pantheon) - Better than GNOME. They are having and developing actual application like geary and midori. You can feel they are actually dogfooding in contrast to GNOME couterpart.
Unity - I like Unity itself. Very long time user. But Canonical lied to us it's stable but actually alpha stage. One more bad thing is it smells vendor lock-in pretty much. Anyway pretty usable and has big ecosystem(community + vendor).
XMonad - At first time, it just looks like another tiling window manager. More I use it, it feels like 'custom desktop construction kit' if you don't mind learning about some haskell. As you all know, 'kit' is about fun and learning more than actual result. So I'm doing still this dumb like window manager ...
I saw those as regular parser that returns text but not just grep wrapper. Yes It has function named 'grep', but its not grep wrapper. It looks like `lstree` could be combined with `grep` function for emulate `grep -r`.
I would rather recommend http://discourse.org for anyone who finding mailing list + nice web and mobile interface.