I've had a Fenix E01 on my keychain for about 6 months now. It has come in handy many times, but I now find myself wanting more than 10 lumens if it's going to be my only light 75% of the time. So I recently ordered a Maratac AAA (should arrive tomorrow). Whenever I'm away from the house, I most likely have my keychain with me, so I wanted a good primary light to live on the keychain.
If I am going anywhere after dark, I take another light with me, always a single cell riding in a coat or pants pocket. Sometimes a Fenix PD20, sometimes a Nitecore D10 R5, but usually a Fenix LD15 (which has one of the best beam profiles I've seen).
For me, a Nitecore D10 is the absolute maximum size I'm willing to carry around in a pocket, and I almost always prefer a slimmer light.