Back on topic, much as I love Hikaru and Go, both.
I started out with Debian back in the late 90s. While studying computer science, it remained a highly useful tool for server use and general programming.
However, what Debian lacked was speedy updates. It is highly stable and secure, which are its primary benefits, but it accomplishes this by (among other things) a very careful (read: slow) update schedule. From potato (version 2.2) onwards, there was a release every two or three years. Once a release was made stable, a new "snapshot" of then-current software was made. If, say, a new version of Mozilla was made available soon after a snapshot, it would propagate into the next snapshot after two-three years, and then finally hit the stable release another two-three years after that. After a THOROUGH vetting of the software and its code.
This made me install things outside of the package management, which made upgrades sometimes wreck "everything". Luckily, I've always tended to keep backups.
Anyway, when I switched from hard drives to an SSD in my current computer, I decided to make the jump to Ubuntu. I haven't regretted it since - everything is (almost) up to date and even older versions get new software releases. I'm using Firefox 10.0.2 right now, which was released a couple of weeks ago, and which will not reach Debian stable for another two-three years, minimum.
I still use Debian for my server, though, but apart from software versions (and some consequences thereof) they're virtually identical from the command line point of view.
As for specific Ubuntu version, I would recommend either Kubuntu or Xubuntu for a Windows user wanting to "dip his toes". Either "feels more" like Windows than current (Unity) Ubuntu, Kubuntu is probably better for a newcomer, while Xubuntu might be better if you have slow hardware.
Why not Arch/Redhat/whatnot? Well, really, my primary reason at the time I made my definite choice (I fooled around a bit with RPM-based distros) was APT, which nowadays isn't as big a deal. However, as has been mentioned by others, the support is rather nice, even if it can be a bit difficult to find the "best" answer in a flood of well-meaning pseudo-solutions.
BSD? Not Linux, but still a valid option. However, if we consider "free desktop operating systems" a very minor subset of all desktop operating systems, then BSD-derivatives are a very minor subset among those. In other words, it's a minority within a minority, and support might be a bit harder to find or understand.
Hurd? Now we're talking...but not yet. Microkernels are a very, very interesting alternative to traditional ones, but it's not exactly stable, by anyone's definition. Feel free to test it, though. It's bound to be an interesting experience.
Anyway, there's my five cents.
TL; DR: I recommend either Kubuntu or Xubuntu, they look more like Windows than vanilla 'buntu and Xubuntu is considerably faster though perhaps not as user-friendly.