Probably the single biggest reason for WP’s success is the one-click install and one-click upgrade offered by Dreamhost and other web host companies. I can literally setup a WP blog for anyone in less than 3 minutes. Most of that time is post-install customization, as well. The plugin ecosystem is far more vibrant on the WP side than MT, and the proliferation of styles and themes means that the end user need only choose from a bounty of available options if they don’t want to tinker on their own but tinkering is also very, very easy since the various files can be edited directly from within the online administration pages.
And re-tinkering is very, very common; I’ve set up three WP blogs, two for myself, one for somebody else, using exactly that DH one-click install, and about every other version, something they’ve done breaks all the customization I’ve done and I have to redo, or at least recopy, a fistful of templates. Meanwhile, what you see here is basically a slightly-souped-up Movable Type 2.21 template that has worked through all of my 3.x installs, though the powers that be Six Apart are careful to note that comment popups are “deprecated,” the current euphemism for “We don’t support that anymore.” I can’t prove it, but I suspect this was motivated by the ongoing penchant for popup blockers.
Still, I have a certain fondness for WordPress, and indeed I once recommended to management down at the shop that (1) they should start up a corporate blog and (2) they should run it on WP. After the “ZOMG PHP!” grousing subsided, the proposal was tabled, and the table was then folded up into a FedEx box and shipped to Lower Elbonia.