I've installed a new, responsive theme to the forum that is mobile-device friendly, and I've set it to be the forum's default theme. I've got the options set to let members choose which theme they use, but I didn't change anyone who had the former theme selected. (About 130 people must have had the "default" theme picked, so it looks as though they were automatically switched over.) The old theme is called "Vertex" and the new theme is called "Studio".
To switch over to the new theme, go into your Profile and then click on the "Look and Layout" link under
Modify Profile in the sidebar. A.t the top of that page it will display the current theme you are using; click on the "Change" link to the right to select the theme you prefer. NOTE: The new theme is available at the top of the list as "Forum or Board Default" (if you choose this option the theme will automatically update if it is switched in the future), and it is also listed at the bottom of the page as "Studio."
Feel free to choose whichever works best for you, but I would encourage everyone to give the new default theme a try. I think you'll like it.