What are some of the ways a beginner can get into Plan9? Can I use it as a Desktop Operating System on my old Thinkpad? What can I do with it? Does it run a modern browser? Could it run QEMU?
I've had much more luck with 9front distribution, it seems maintained at least.
A desktop OS is a vague term, but you have to be super undemanding to use Plan 9 in the modern environment. If you plan to develop on it, be aware: it's quite possible, but it is not POSIX-compatible, it has its own, often quite opinionated tools (Acme editor with its obsessive three-button mouse usage is something I could not get used to), it is often a world-in-itself. It has C, Go, Mercurial, Python though. Don't expect many opensource projects we take for granted to be available (databases, servers, etc). However, 9front has its own "repository" [0] that has ssh, vim, ghc and other basic Unix tools.
No, neither Plan 9 nor 9front run a modern internet browser. A modern browser is a complex, non-portable, monolithic, demanding beast. It just does not fit the Plan 9 vision, so the common piece of advice is to run a VNC session to a mainstream OS to browse the internet. `elinks` is "a graphical browser" according to Plan 9 people (and I rather agree).
This is impression of a beginner, so feel free to correct me.
[0] http://www.plan9.bell-labs.com/wiki/plan9/Contrib_Index (oops, it is offline at the moment).
I love emacs so, so much (I'm the nerd who has foot pedals, and I've spent at least 1k hours perfecting my .emacs.d over the last 10 years). It's ability to meta-modify itself is incredible.
Editor rant for nerds who have spent at least 100 hours on .vimrc or emacs.d:
But ACME takes it to the next level. It feels like Smalltalk. It exposes all buffers via a FUSE block device you can mount, and all of a sudden you can feed buffers or sub-selections of buffers to standard UNIX utils. Literally everything that takes input from STDIN you can pipe to, and optionally return to the same buffer via STDOUT. You're no tied to languages. Hating Vimscript or Elisp becomes irrelevant because as long as you can run the binary and pipe to/from it, you can manipulate your data.
It's fantastic for exploratory scripting, literate programming and my only qualm with it is I'm a home-rower. (That is, all of my interfacing revolves around keeping my wrists and about 1/4" of my lower palm. My wrists are planted in that specific position 98% of the time, with movement primarily centered around pivoting my wrists about those two radial points).
My idea is to use Caps as a meta-key, then have s,d,f act as 1,2,3 on the mouse. Even with chording, it doesn't impose a stretch.
If you are passionate about editors, watch Russ Cox's talk on ACME. https://www.youtube.com/watch?v=dP1xVpMPn8M.