Not sure if this helps, but here's what I wear:
- old Brooks running shoes, size 10.5: these fit snugly, and my foot fills the entire thing.
- cheap K-Mart black leather shoes, size 11: these fit well.
- Nike Zoom Waffles, size 11.5: these are very narrow and long, and fit nicely excluding the extra length in the toes.
- Asics Tai-Chi's, size 11: similar to the Zoom Waffles, but less extra toe-space.
- Rogue Do-Wins, size 10: bit loose in the heel, otherwise awesome
- Adidas Ironwork II's, size 10: far too tight in the toes, pretty loose in the heel, these are brand new and I intend to either resell or return them
- Vibram FiveFinger Sprints, size 44EU: I measured between a 43 and a 44 when I bought these, decided to go a bit larger in case I grew at all; they're a bit long in the toes and have some extra heel sticking out, though once I had worn them for a few weeks, and learned to put them on, this became a nonissue
- Vibram FiveFinger Flows, size 42EU: this time, I measured an exact 42 (equivalent to a 43 Sprint) this time; I think my foot arches may have risen from wearing the Sprints so much, making my feet a bit shorter; the shoes fit snugly and my toes near entirely fit the boxes, with no excess heel - a real great fit