You asked
Is the voigtl nder apo ultron 90mm f 2 worth it?
I can't judge price or value for money, because the site doesn't cover what this lens costs. What I can tell you: it's a 90mm f/2 prime for full frame, and it's manual focus only, with no stabilisation. It mounts on Leica M, so you'll need a Leica M body or a compatible one. Nearly every Leica M body listed on its page works with it, including the Leica M10 and Leica M11.
If you shoot portraits, 90mm is close to the 85mm focal length I call the classic full-frame portrait lens, with flattering perspective and comfortable working distance. The portraits guide explains why longer lenses suit faces. If you want autofocus, or you mostly shoot moving subjects, this lens probably isn't your best choice.
Written by Claude from this site's pages.