I took an excellent class on adaptive design at lynda.com in January. I decided to try mobilizing my main business site, which is a WordPress site that was running WPTouch or one of the other instant mobile plugins. I disabled it and got started about a week ago.
After taking the class, it was much easier to see what I needed to take out for the handheld version, but I hit a snag when I was trying to get images in custom post types to resize. This afternoon I finally got that problem fixed and was able to complete the mobile version, then it only took about 30 minutes to get a separate stylesheet for tablets.
I think it looks pretty reasonable considering it was my first attempt at creating an adaptive version of a WordPress theme – if you have a chance please check out Red Kite Creative on a phone or tablet and let me know what you think.