I just love the Voigtländer lenses because to use them is a joy and image quality is very very good. I own a lot of these and I haven't found a lens lacking up to the Heliar 75 f2.5. Above that, in my opinion, the Voigtländer lenses start to deteriorate. I have the 85 f3.5 which I think is the worst Voigtländer lens I have used. I also own the 90 f3.5 which I find difficult to warm up to. maybe I have bad copies of both but I'm now going to test or exchange them for better copies, as I have other better lenses in the focal length range.
But all the others ranging from the 15 f4.5 heliar to the 75 f2.5 heliar, all are great lenses. On some of these lenses, like the 35 f2.5 Skopar and the 40 f1.4 Nokton the construction also includes the thumb lever for focusing. I think this is one reason I don't use these lenses more, I just hate using it. This thumb lever is found on Leica and rangefinder lenses also and I suppose somebody thought it a good idea to incorporate it into the lens design. I personally just can't get used to it and it just gets in my way. Apart from that I just can't fault these lenses, and the solid construction means these lenses will be with me for many many years to come. One final thing I have to mention is the price you pay for these lenses is very reasonable, in my part of the world you can get them for €400-€500. Try and purchase a Leica lens for that price.