In the current release, the text font in vertical tabs was increased to match Safari's. Side by side comparison:
In safari, this font size is fine as it is not meant to hold too many items in it, usually around 5 to 10. However, the Orion Vertical Tab Bar holds tabs, which can be upwards of 50 items. With tree tabs, the problem gets worse as it gets harder to read the tab's name.
Please revert the font size back to what it was previously.