Ark and arch are two different distros - this used to confuse me as well. To see current packages, just go to
http://www.archlinux.org and click on the package list for noodle. Those things in Current, Extra, and I believe even Community are the "officially supported" packages -- sort of like Ubuntu has -- though I don't know what that really means in a community distro like Arch. The other repos tend to be testing repos. Community has to be enabled in your /etc/pacman.conf though, so it may not be officially supported after all - again, I have a hard time with this concept.
Other than those, there is a huge wealth of stuff available as compilable packages that pacman will manage in the "AUR" (
http://aur.archlinux.org/packages.php) -- these are not officially supported but a number of the packages have been signed off on by Trusted Users. This is sort of like ubuntu's Universe and Multiverse taken to the next extreme - people wanted the stuff for themselves, and made a pkgbuild for the software for themselves, and decided to shae it with the community. If software is popular enough here, and has been deemed safe, at some point it may get moved into the Community repository.
There are also a few packages (I had to ask about this on the forums myself) that are like checkinstall. Download the source, run configure, and make, and then the checkinstall-like command (there are a few - I'm using creapkg right now, and have found it quite satisfactory). This gives you a package you can manage with pacman. And FWIW, compiling on arch is a dream. Just remember that /opt is preferred over /usr/local by arch.
I can't speak to lappy support, though if my Workstation Migration goes as planned, it probably wont be too long before I get arch on there as well. Honestly though, Kubuntu works so well OOTB on my lappy, it's probably going to take a while before I get the urge. Or not. I guess we'll see.
Yes, it has XFCE, though IIRC, XFCE has started recommending that you download their installer and just install it yourself.
If you have a testing PC or a spare drive, I'd really recommend trying it out and going from there. It may not be for you, or you may fall in love with the Arch Way. I certainly fall, at least in part, into the latter camp. I've started remembering why I started using Linux in the first place -- I have control over my OS. Yes, there's a fair bit of tinkering that needs to be done, but even a lot of that is voluntary. The defaults work quite well, or at least they have for me so far. IMO, their new hardware detection daemon (is it actually a daemon? Maybe that's a poor choice of words) "hwdetect" is so much better than hotplug, it's like comparing rocks with rock candy. HWD and lshwd are also very impressive and still very useful, too. I'm not at all a boot-time whore, but it's nice to be up and running in under a minute - generally in about half a minute. From me, arch gets two thumbs up.
Also, if you *do* decide to install, get a copy of the new 7.1-pre installer. It's a lot easier to deal with than the 7.0 installer. It takes care of the problems surrounding the devfs to udev conversion, and it also takes care of the newer migrating to initrd. Absolutely painless, especially if you let their automagic disk tool partition your drive for you.
Shared pain is lessened, shared joy is increased; thus do we refute entropy.
--Spider Robinson