Well, I agree with you that Ubuntu does lack some features that are desired in a good streamlined OS, however stating that it is useless is completely giving out the wrong information on the subject. Ubuntu is linux, and under the hood it runs Linux. Meaning you can run just about any Linux based app on it that you could with any other distro out there. I would say you probably meant is minimalistic, which IMO makes a better OS anyways. However, Debian based Linux distros do some things that don't quite make sense to me. However, Ubuntu is by no means a useless operating system, and it has done some great things for Linux and the Linux communities.
Nope, Intel's first 64bit desktop processor was the Core 2 Duo ( I believe, someone correct me if I am wrong). So you will need to go with the 32bit version.
Are you planning on ever recording TV, if so I highly recommend Myth TV, which runs on Linux.
www.mythtv.org
Well the pros would be it has higher memory addressing abilities, and can utilize higher end hardware. Other than that, there is really no big difference. You may run into some compatibility problems with legacy (32bit apps) on a 64bit system. However, most things that you might want to use will be updated to support 64bit architecture.
