...how easy is it for a reasonably intelligent but not particularly computer savvy individual to get to grips with Linux?
No harder than DOS.... Joking aside, a good distro like Ubuntu or SuSe makes it pretty easy
...as a user of several expensive bits of Windows software (AutoCad, SolidWorks and a handful of odd computational fluid dynamics programs.....
These don't port easily - stay with Windows for the moment
.....My current XP machine is stuffed to the gunnels with odd bits of useful stuff, like umpteen Excel spreadsheets for doing odd bits of aircraft design and analysis, plus lots of Word reports, templates etc. Does all this sort of stuff port across to Open Office on Linux reasonably well?.......
OO copes very well with simpler documents, but stumbles over complex documents with embedded stuff. No surprising, because MS keeps the formats secret and it all has to be reverse-engineered. Stay where you are for the moment.
......I guess I could try it out by converting my spare PC to Linux, whilst keeping the XP machine going, but if Windows emulation is reasonably good then maybe I might be able to completely cut free from MS domination (that certainly appeals!).
Thats the way to go. Learning Linux isn't difficult (people coped with Windows for Workgroups which was a lot worse) but it takes some minor effort - well worth it though!