My greatest pet peeve with most themes, and most web sites actually, is that they are designed to have a fixed width layout, and most web designers could not care less about XHTML and CSS compliance validation.
I don’t understand why web sites and/or web authors should decide on the optimal width of my web browser’s window. It seems so inflexible that sites are designed for 1024 pixel width or 800 pixel width. What if my browsing device is a 320 pixel width mobile phone? How difficult it would be to try viewing a site that insists on 1024 pixel width on a small little screen! Okay I realize there are also people who are strongly opposed to fluid width for various other reasons. To each his own. (So that’s why I spin my own theme.)
The next thing is about standards compliance. I have a thing for adhering to established standards where possible. Standards are established to serve a greater good. The only time I think it is justifiable to deviate from standard is when it fails to meet the needs of the greater good.
Simplicity is my first attempt with WordPress theming. I also rarely work on PHP (most of my web development uses Perl). So configurable options and such are currently almost non-existent. But these will improve with time. I just wanted to get something out of the door to get some feedback.
You can also watch for updates of Simplicity on the WordPress Theme Directory.