They are drop dead gorgeous bicycles.
I've been tempted by De Rosa Pistas, but ultimately I wouldn't ride one that often.
I don't have enough healthy tissue in my left knee to do it, and I can't imagine dragging one out to the local paths.
..nor the Velodrome for that matter.
Last time I did that I ended up having fluid drained from my knee.
They'd make fabulous wall hangers for me, but I've got one or two of those already.