What's more important: Form or Function?

Recent news surrounding popular blogging platforms has focused on their ability to help users "design" their blogs. And it made me wonder, how much will the availability of themes influence the choice of which platform to use? Is it one of the first things you look at, or do you look into designs only after finding all the other features you want?

Below is an assortment of theme selection pages for various platforms.

TypePad: http://www.typepad.com/go/design-assistant/

Movable Type: www.movabletype.org/design/assistant/

b2Evolution: http://skins.b2evolution.net/

WikyBlog: http://www.wikyblog.com/Special/Main/Templates