Flat and flat enamel are different. In areas that are out of reach and can't be touched, flat is the way to go if you don't want any reflections. It will scuff with the slightest touch however, and touchups are kind of a pain. I used it on everything that needed a dark color but would be covered, like my false wall framing and fabric frames. Flat enamel definitely has more of a sheen, but not too bad. It does show scuff marks, but they are easier to clean. You can't scrub it, but you can carefully remove scuffs. I used it on my soffit which sits fairly low, especially over the riser. I didn't want to deal with finger prints. For a high ceiling that could not be touched, I would use flat instead of flat enamel.
For a little extra protection and ease of cleaning, I'm using eggshell on my trim and door. All 3 sheens are the old Mouse Ears mix, now simply referred to as Behr "black". You can get all of them in either Premium Plus (no integral primer) or Premium Plus Ultra (primer mixed in). I haven't heard many good things about the Ultra so I've been using the Premium Plus.
Edited by Spaceman - 11/1/12 at 8:51am