Barry;
I think you did the right thing in purchasing the 5omm Summicron. Even tho' it's the same focal length as the Noctilux, as the above posts mention, then Noctilux is really for a different purpose (wide open).
I have an older model Noctilux(separate hood) that I love, but in truth, I rarely use it. The 50mm Summicron, on the other hand, is what I use 9 out of 10 times.
I have the current Summicron, and find its barrel action to be the smoother & lighter than the previous model (same optics, different barrel). I missed not having a handle, so I had Reinhold Mueller attach a handle.
Regarding not using a UV filter - yeah, I have to agree in leaving it off. For years I used one to protect all my Leica lenses. Like you, I feel vulnerable without one.
However, I've had some heart-breaking incidents where I'll have a shot I really love, and the filter caused a merciless flare. I experimented recently with the 90 ASPH in bright sunlight, with and without a UV filter (a top quality Rodenstock). The flare with the UV filter on, even with the shade deployed, was shockingly visible. So, no more UV filter for me, unless I absolutely need it (e.g., salt spray, at a beach, etc).
Marco