A simple recompile will not produce a 64-bit application, but rather a 32-bit application recompiled for a 64-bit platform. In fact, 64-bitness in and of itself is probably a net lose for an application that's already satisfactorily running in a 32-bit environment, because all of a sudden it's slower and bigger.

My main gripe with Gentoo (apart from the crawling horror that is the installer) is that the main reason for running it (lots and lots of software, all designed to work together) is torpedoed by the crappy package QA. Also, compiling everything gets really old the moment you hit any serious amount of C++; Mozilla/Gecko and OpenOffice spring to mind as particularly tedious. You're a KDE fan? C++, all of it.

Honestly, you're better off with Slackware if you want to fly THAT much by the seat of your undies.

You sound like a Debian Unstable kinda guy. That, or get your Kubuntu pointed at the Breezy Badger release; that way you'll get the oohshiny with more of the wooandyay and less of the lookmaIbrokemypooterandnowitwontbootcuzld.soisbroke.

64-bit is actually really dull. It looks, smells and tastes the same as 32-bit (but with the aforementioned slowness and occasional hilarity(by which I mean extreme foul moods) caused by applications that assume 32-bitness). I discovered this when moving from VMS on VAX (32 bit) to VMS on Alpha (64 bit).

64 bit addressing comes into its own, thought, when you're talking storage. Very Big Disks need 64-bit pointers to address all those lovely terabytes.

If you do decide to plunge into Ubuntu/Kubuntu, and get stuck, gimme a yell. There's plenty of folk around here running it; you'll be well-supported.