I've been playing with Linux (64-bit releases) on my Athlon 2650e 1.60Ghz, 4GB RAM, 320GB HDD notebook recently and here is what I have found. The notebook is a cheap eMachines that runs surprisingly well for what I paid for it and it has a 64-bit processor and also AMD-V for VirtualBox fun.
I've had my ups and downs with recent Ubuntu releases. Usually, 99% of everything would work, but that 1% that didn't would annoy the hell out of me. After using Ubuntu 10.04 for three weeks, I had found that everything actually works! The changes they made to the UI are arguable to whether they are good or not -- the biggest being the move of the window control buttons from the right side to the left side. I can live with that one. Otherwise, the UI work that was done to Ubuntu is fantastic -- thank goodness they finally de-browned the UI. I have nothing against the color brown, but previous Ubuntu UI color schemes were horrendous. The new purple + orange scheme is a lot better. The boot times for Ubuntu 10.04 are really quick (I'd say 10-20 seconds) and the general feel of the OS is snappy (yes, I know "snappy" is not scientific). The "me menu" is a bit bunch of hype and I don't really use it that much.
A week ago, I installed Fedora 13 over my Ubuntu install and ran it for a week. Fedora is a mixed bag for me. I have been a Red Hat guy for a long time and run CentOS on my server and like having the stability of CentOS/RHEL. But, I am finding that I am only a Red Hat guy when it comes to servers. Fedora is cool because it is cutting edge stuff (really? btrfs? cool!) and also because it has some really nice technology in it (I really like the yum-plugin presto that does differential package updates). One of Fedora 13s coolest addition is the automated printer setup. There were other small issues with Fedora 13 (like a Cheese didn't work), but overall everything worked well. The boot times for Fedora 13 are nothing to complain about, but they are slower than Ubuntu 10.04. The general feel of Fedora when using it as a desktop OS is "solid" (which, to me, feels slower than "snappy"). And the UI for Fedora does not wander much from a plain Gnome install -- which can be a great things for some people.
I reimaged my notebook back to Ubuntu 10.04 last night. Not because I don't like Fedora, but because I am using my notebook for regular stuff -- webbrowsing, mail, some programming, editing docs, ssh'ing to different boxes and VirtualBox tomfoolery. Nothing that needs the super cutting edge technology that comes in Fedora. So, having a nicer UI is more important for me than having the bleeding edge features -- sure, it woud be fun to play with btrfs, but on a day-to-day basis is it going to make a difference?
This doesn't mean I'm giving up on Fedora 13, it is just going to live a quiet life in a VM on my Ubuntu install. And I will play with it to see what cool stuff is in there. But, for normal use, I am going to stick with Ubuntu 10.04.
One last thing, since 10.04 is a Long Term Support release, I can customize the hell out of my install and not have to worry about having to upgrade in 12 months. One thing after that one last thing. Ubuntu 10.04 doesn't work on my Toshiba netbook (neither has previous Ubuntu releases). Not sure why they can't get sound working properly.