The 'inconvenience' of passing through other PCs was one of the things that really pissed me off in FFXI. It was especially annoying in crowded areas. I hated running through an AH area, coming to a halt, realizing that another player is loading there, then pushing through as they load in front of me, then seeing it happen again 2 steps later. I don't know how I feel about terrain collision detection, but I am against collision detection with PCs. If you want that real life feeling, then when I hit another PC, throw them off balance for a second and make them give me an automatic middle finger reply.