Are myth upgrades usually painfree? I have never had to go through a version upgrade before, but I would hate to have to fiddle with my current setup (although I probably won't be able to stop myself from upgrading). We only have one TV in the house, so it would be rather 'inconvenient' to have it out for any lenght of time.
The difficulty of the upgrade is dependent on lots of things, OS and hardware being the most likely area for problems. The new version may have dependencies that your Linux distribution may not have, and your hardware may or may not be supported, depending on the age. I can't really speak to any upgrade issues as I am always running pretty much current trunk revisions (usually update once a week or so) and I haven't had any real show stoppers, and in a few cases I've helped to find bugs.
As for Windows, again I can't speak to it as I don't use it, but from what I've seen on the commits list, there has been a fair bit of work to make it easier to compile.
I'm not sure what is meant by 'remote capabilities'. Are you talking about remote controls, or remote viewing of some sort?
Well, couldn't resist. I upgraded today and it seems to have worked. I had to delete some existing theme files first, and then had to run some database update. Seems to be working so far. Just missing the theme I was using before, but I assume I can find it somewhere.