Loved my Archimedes
Just like the BBC Micro was the world's best 8-bit micro, the Archimedes - for about a year - was actually the best PC full stop. It wasn't until Intel brought out later generations of its chips in the late 80's that they finally overtook the Archimedes. I never bought a second Archimedes model because I felt that the performance difference wasn't good enough and the gap just widened over time.
Again, like the BBC Micro, Acorn's developers did a fantastic job with the OS - a great (and extendible OS), a much enhanced BBC BASIC and keeping a built-in assembler meant that serious development was possible on the machine you bought. Although paying 50-odd quid to upgrade your ROM set was a stinger back then, it meant that boot time remained 2 seconds, which trounced every other IBM PC clone out there.
Arm (!) yourself with the multi-volume programmers reference manuals and you'd have years of quite fun programming ahead. My greatest efforts were:
* A VT100 terminal emulator written in 100% ARM code that identically matched the behaviour of a DEC VT100 I had access to (including smooth scrolling [in software!], double width/height, flashing etc.). It's extremely rare for anyone even back then to write a terminal emulator entirely in assembly, but I did it.
* Hacks for various games, including completely reverse engineering the codes generated for the Zarch competition that I think was announced in Acorn User. I'd already generated the codes for a massively high scoring game but didn't submit it for fear of being found out. I wonder if the winner did the same thing as me!
* Writing a Scrabble game in a mixture of BASIC and ARM so I could enter the 100 quid Daily Telegraph game (it always found the correct answer). Couldn't release the game because of the terrible copyright hounds of Spears/Hasbro.
* Removing copy protection from games, though I got bored when Magnetic Scrolls The Pawn decided to use a "page 7, line 14, word 2" type protection and also released their game compiled in C (possibly one of the first ever in C?!), which produced such awful ARM code, it became its own form of copy protection :-)
I did eventually tire of the Archimedes though, but I clung onto it for so long that my next machine was an HP PA-RISC Unix workstation followed by an Intel PC with Linux a few years later. I'm still proud today - running CentOS 6.2 on my desktop at work and home - that I can say that my primary desktop OS has *never* been Windows on any machine I've owned.