WordPress has one nice thing — themes support. Effect is that I change theme from time to time.
In most situations I modded theme for my own style each time. That made upgrading to newer versions harder but was worth most of time. What was changed? Removal of categories (which I do not use), replacing them with tags, removing not useful elements of page, changing CSS etc. Those changes which could be useful for others I usually sent back to authors.
Before this theme I used Atahualpa but it was overloaded with options and still used tables for layout which I find too deprecated. And lot of extra code was generated and inserted into page each time. And I had lot of problems when tried to upgrade to newest version.
Now my blog uses Carrington Blog theme and as usual some changes were made to it. I like that theme and it will stay like that for some time (until next change).