I have owned and used many CV lenses over the years. And they have all, without exception, been perfectly good lenses limited only by the skill of the photographer. They are all exceptionally good bargains compaired to Leica lenses.
But I have also either sold, or will sell (in the next months), them all. Because they each had some little thing that I didn't like that pushed me over the edge to eventually buy (or keep) the more expensive Leica alternative.
The 35/1.2 is too big (got a 35mm Summilux ASPH), the 28/1.9 and 28/2 are "not bad", but the 28/2 Summicron ASPH is way crisper), the 50/1.1 is a Noctilux wannabe, but not quite there, the 75mm f/1.8 Heliar only focused down to 0.9 meters (bugged me and I already had a 75/1.4 Summilux), the 40/1.4 and 35/1.4 each had funky bokeh in my opinion and the buid quality wasn't quite up to scratch (I stuck with my 40/2 Rokkor-M and 35/2 Summicron)
If I ever need/want a 21mm lens again, it WILL BE the 21mm f/1.8 Ultron - it was AMAZING on the Leica M9. I only sold it because I very rarely need anything that wide, and it was TOO BIG to carry around for just rare use.
If my 35/2 Summicron ever dies, I will get a 35/2.5 Color-Skopar - it was so tiny and so great.
Last, the 75/2.5 Heliar is fantastic. I see no reason to get the Leica Summarit over it. This will possibly be the one CV lens I end up keeping for those times when the 75/1.4 Summilux is too big to lug around.
Film for B&W, digital for colour