Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
The latest version of Ubuntu, Raring Ringtail, is billed as business and user-friendly. There are still significant obstacles to its widespread adoption in the enterprise, but if your employees only access applications via the browser, and your company doesn't use complex spreadsheet macros or document formats, then Ubuntu 13 might be worth considering.
We had no trouble installing it from scratch, and no trouble upgrading from the previous version of Ubuntu. Installation took about 20 minutes total, we saw no driver issues, and Wi-Fi worked right out the box. MP3 support is not included by default, but is an option during the installation process.
The biggest problem we had with our initial install was that we couldn't run Google Chrome. The open-source version of the browser, Chromium, worked fine. The Google Chrome dependencies problems were fixed in late May, however, and we were since able to download and install the browser.