Sorry, I'm not quite ready for Linux just yet. If I drop Windows it is not going to be for another platform that requires full-time tweaking! At least on a Mac I wouldn't have to tweak very much, if anything.
That hasn't been my experience with OSX. Hope your Mac experience offers smoother sailing than mine. My first Mac (SE30) ran System 6.0.4. That wasn't exactly maintenance free. Nor have any of the other iterations (from 7.0.1 right up through OSX-Leopard) been what I'd consider set & forget systems. Ditto for their hardware. I do tech support and service on Apple products, and I use one, so I'm not basing my opinion on propaganda from Bill-G or Tux. Apple makes a fine product. But Macs can be skittish. Like all Thoroughbreds.
I'm also not sure what you mean by full-time tweaking. Linux updates are available for download via a system updater just like you have on a Windows or Mac box. You're not required to do anything if you don't want to. Many Linux users install their distro and use it "as is" without ever changing anything. That's the beauty of the beast. You do as much or as little system work as you're comfortable doing. Tux keeps on chugging either way.
There's also a thing called WUBI that lets you install Ubuntu almost as if it were an application. If you don't like it, you can just go to your Add/Remove Program control panel and uninstall it like any other app. Doesn't touch your Windows environment at all! Great if you just want to get your feet wet, or make up your own mind instead of listening to what the rumor mills (and me for that matter
) have to say about NIX.
Either way, whenever (or if ever) you're ready, Tux is waiting with open arms.