Witch 4.5.1 is out, with only a few changes—Witch can now see tabs in Opera, we worked around a bug in Finder when using a frontmost-windows-only switcher, and we resolved an issue with Chromium-based browsers that caused their tabs to be invisible to Witch.
You can read the full release notes, but they basically say the above in a few more words and with more line breaks. As usual, updates can be found by checking in the Witch System Preferences panel, or by downloading Witch from our site.