I'm another Arch user. It's a terrific platform and very stable--something that isn't always synonymous with a rolling release. I think my affinity comes from the rapid updates to new package versions more than anything, and the fact that its relative simplicity in design and implementation is somewhat analogous to the BSDs. It's also very much like Gentoo--I think the two share many things in common, at least in spirit, even if their implementations are hardly alike.

I first used Arch about 2 years ago at the insistence of someone on Slashdot. I was reluctant to try at first due to the comparative weirdness of pacman ("weirdness" is relative) but found myself quickly hooked. I only wish I could remember the username of the kind soul who pointed me toward Arch. I'm indebted to them for being so kind as to offer suggestions to my repeated prying, and I hope that I can one day extend the same kindness toward someone else.

However, it's worth mentioning that Arch isn't necessarily for everyone. You must follow news updates periodically and keep an eye out for updates that may require manual intervention. Worse, if you're lazy and fail to update the system for a significant period of time (usually 6 months but typically 1 year or more), you might encounter circumstances where upgrading the system is difficult or can only be performed in stages with intermediate packages. The disappearance of arm.konnichi.com (sort of a roll-back machine with older packages) sadly makes incremental updates of older systems difficult, but I think the final set of transitions to the latest file system layout bringing Arch up to par with many other distributions that are currently undergoing the /usr merge effectively renders many of these problems moot. But, if you're studious and regularly update the system, you'll rarely have any issues. Suffice it to say that like what dizzystar wrote, Arch often stays out of your way, but it does need a little lovin' now and again.

My first exposure to F/OSS operating systems was through OpenBSD and FreeBSD, and although I later migrated to Gentoo, I've always had a fondness for the BSD spirit of simplicity and fantastic documentation. After Gentoo, I again migrated to Arch and haven't looked back. The regular recompilations in Gentoo, particularly of X, KDE, or Firefox, started to wear me down and sent me looking for alternatives, but I couldn't bring myself to adjust to Ubuntu or its kin. That's not so say I dislike Gentoo, of course. I really do enjoy Gentoo, even now, and I greatly appreciate the work the Gentoo team does (I still make use of Gentoo for a few things, mostly in virtual machines); I just reached a point where I wanted to enjoy the benefits of a rolling release distribution with the benefits of binary packages, and my time availability is a little less than it was when I used Gentoo. Arch is in some ways much more automated than Gentoo (and in other ways, it requires more manual labor), but all things considered it's the best of two worlds: Rolling release and binary distribution.

Arch with KDE is probably one of the best combinations you could ask for: You benefit from eye candy, usability, a fantastically stable platform, and updates to software packages almost immediately after their release. Moreover, the philosophy of Arch is one of keeping upstream packages as vanilla as possible, so there's little that needs to be done in terms of eradicating obnoxious and invasive package customizations. Even larger packages like KDE are identical to what you'd get if you compiled the sources yourself. I can't say the same for other rolling release distributions like Aptosid which customizes so many of the base packages, it takes time to reconfigure things if you don't happen to have a preassembled set of dotfiles to copy from (which you should anyway). But, I'm not much of a fan of Debian-based systems, so I'm certainly not free of some selection bias.

Ultimately, it's really about what's the most familiar to you. If you like Debian, stick with it. If you like Redhat, stick with it. If you like the BSDs, Arch or Gentoo might be a good bet. If you don't want to spend any time learning Linux distro internals, sticking with a "training wheels included" OS like Ubuntu or Linux Mint might be better options. Arch has the advantage of the Arch User Repository, though, so the selection of software available to Arch users is far superior to many other alternatives.