mail(1) or nedmail(1) is all I really need.
I prefer mutt/neomutt, but Thunderbird comes by default in basically every desktop-oriented distro I regularly interact with, so I end up using that most often on *nix. K-9 if I want it on my phone.
My true love is the combination of acme(1) and faces(1), but that doesn't do encryption/PGP stuff.
You are correct and this can be seen in some of the old AT&T demos from the '80s floating around on YouTube. There is even a chart that specifically labels a directory like /usr/bwk as the user's home.
Plan 9 also uses this old convention; users live under /usr and there is no /home.
Sure, basically any Debian-based distro should have gdebi in its repos.
It used to be that everyone in the Boot Camp got their own VM that was wiped each season, but recently everything was migrated to a single installation that doesn't reset and everyone uses.
In short: now you get a permanent account.
And yes, SDF itself is NetBSD-based—the largest single installation as well as a primary testing environment, if I'm not mistaken.
Python 2.5.1 was distributed as part of 9front back when it used hg, but it was ultimately removed from the base system once we switched over to git9. 9legacy still packages binaries, however; they're up to 2.7.6 for Python and 2.9.2 for Mercurial.
I never bother with venti/fossil, honestly. I'm more of a cwfs kind of person, but Ori's gefs has been attracting my attention lately.
If you ever want to just poke around a Plan 9 system, SDF Public Access UNIX System offers an ongoing Plan 9 Boot Camp.
Stop by and join us in com sometime!
Additionally, for those that may want a Plan 9 that's being actively developed and will actually work on modern hardware:
There's also 9legacy, which is basically "classic" Plan 9 with some patches from 9front.
I use it because it's truly a "complete system" in a way that Linux and even the BSDs are not—every program is an example in itself and it comes with a ton of various scratch-built utilities that you don't usually find as part of a typical Linux distro. Stuff like a basic torrent or IRC client just sort of fall out of the way Plan 9 is organized and implemented.
It also provides me with a distraction-free environment and a set of tools that I enjoy using, even if some aspects of Plan 9 as, say, a laptop daily driver are inconvenient or awkward. It really is better suited for networked computing.
I was pretty much sold from first contact because Plan 9 is the way that I feel best matches what I've always wanted from my machines: a simple grid of networked appliances where I can route the various resources and hardware in whatever way I require.
Love the tailpiece! Rustic simplicity at its finest.