I recently upgraded my eight year old site to use a responsive design, making it mobile-friendly. I’ve kept the basic look of the site, although I retired the header image. The site is more readable, both on desktop and mobile devices.
Most of my traffic is desktop — presumably because my readers are computer programmers and engineers — so there wasn’t an urgent need to upgrade. On the other hand, improved readability and improved google search ranking may increase my mobile traffic. Whether mobile traffic increases or not, I am happy with the more modern design.
Mobile-friendly means the site will also respond fluidly when resized in a desktop browser window. This is useful, for example, when you want to keep one of my converters or calculators up on part of your screen.
There are still some tweaks to make, mainly to fix minor formatting issues, but the experience should be good. (Landscape mode will generally give the best results.) If you encounter any problems, please let me know.