Recs.
Updated
The Common Desktop Environment (CDE) is a free desktop environment for Unix and OpenVMS, based on the Motif widget toolkit.
SpecsUpdate
Pros
Pro Mature
CDE was developed more than 20 years ago to work as a unified DE for all the various forms of commercial, proprietary Unix operating systems that dominated the market back then: AIX, TRU64, HP-UX, Solaris, IRIX etc...
Nowadays it's released as an open source Desktop Environment for Linux. It comes as a free tested, widely deployed and enterprise-level product even if it's recently re-release as FOSS for Linux.
Cons
Con Outdated UI
The graphical interface is very outdated and ugly. It's mostly for lower-end machines and for people who want to give their Linux machine a true UNIX feel.
Recommendations
Comments
Flagged Pros + Cons
Con There are no cons. It's a choice. It works. It is only dated in the eye of the beholder.
Anyone who says it's "dated" or that it's only for lower end systems, well that's an opinion. It runs fantastic on higher end systems.