My only comment about segmented memory is that it's a bit of a fiddle to set up. My default mode is to just do without, but when I do use it I have to switch down a gear because of the setup, and generally I never get it right first time. It just gets in the way of my workflow a bit, but equally, it's a damn fine answer to "how much deep memory is enough?" because in some very sparse scenarios effectively you have almost unlimited memory.
Given the choice between, say, 4Mpt/ch with segmented memory and 20Mpt/ch without, it's a tough choice because I want it all! I guess in the end, segmented memory realistically gives you more options as long as you have a reasonably repeatable scenario to get your triggering, timebase and segmented memory just right.