At home, 100% Linux. The closest I come to Windows is Win2K set up in a VMWare session that gets treated as an "application" for a couple of scanner-setup programs!
I do have to use Windows at work, that's what all the software we use runs on.
But I'm not a rabid anti-MS zealot like many Linux users. I just prefer the freedom to do what I want with my system! If I could get the total customization in Windows or OS X that I do in Linux, maybe I'd still be running one of them but I really miss things like "focus follows mouse"... :-)
As to which Linux, I started with Slackware back in the dark ages (something like 1993-94). Fiddled with Red Hat a bit for desktop use, but by the time they went to Fedora I wasn't happy with it. Now I use Ubuntu for desktops, and Slack on my servers.
I would even stick with Slack on the desktop, except I also like to just randomly try apps here and there and got tired of having to track down some random library (or ten!) that the author wanted to use every time I did it. Synaptic makes it easy, and has an incredible number of packages available at a single click. Only thing I had to compile myself is the software that interfaces with my shiny new weather station! When it comes to the servers, though, I hand-configure them so I know exactly what's going on.
But I think your premise may be a bit flawed. I would NOT necessarily expect tinkerers of the windmill-making variety to necessarily be tinkerers of the software variety. There can be some crossover, but in my experience those who are very skilled with fabrication (I work with lots of fitters, welders, so forth) are frequently not computer people. They may use one, but they aren't all that into it. On the other hand, many true computer geeks wouldn't know first thing about welders and machining and woodworking.
I'm somewhere in the middle. I know just enough of many things to be dangerous but not really great at any of it... ;-) (Jack of all trades, master of none...)