Pfft, easy to update. Updating is a sinch. I used to think it'd be hard, but even dramatically updating the style (like the Webmaster-Talk I did), most templates are still default.
vB uses a kind of 'fall through' template system. Say the forum looks for a template 'postbit', if it's been edited in the current style then it is returned, if not it returns the default (or parent) styles tempalte. You can think of a child template being on the first layer, and when the big vB "hand" comes down to grab a template, if it isn't there then it just goes down to the next "layer":
Code:
Layer 1: Custom, Layer 2: Default
Layer1: -------- postbit ----------
Later2: FORUMOME postbit SHOWTHREAD
So the system see's no updated template in Custom, so it "goes through" and fetches the Default (parent) template.
Anyway, you probably already knew that but my point is, when you upgrade the default vB style is updated and thus, so is the majority of your style. You then just have to go into the thread at vb.com and search for updates to a template that _is_ edited, the most I've had to do with the DevBox style is update the 'logout' link to put in the userid.
So I think it's worth it, if you didn't get that message out of my babble
