Re: Metric vs. Imperial: While I hold some of the key conversion factors in my head, the Imperial system of weights and measures is *vastly* easier for me to visualize because I (and, I would guess, most Americans) have no practice with the metric system. I know what a gallon looks like through long experience (there's always one in my fridge); I know what a liter looks like only by reference to a gallon. Similarly, I know what a 10' x 15' room looks like because I'm in one roughly that size every day. As an American, I find, for better or worse, that the Imperial system is part of my daily life and the metric system is not. I find games using the metric system very cumbersome because I have to make on-the-fly conversions in my head just to visualize things. I can well imagine, if the situation were reversed, that I'd be seriously put out.
Re: Miniatures vs. No Miniatures: Since bygone OD&D days, I've made only sparing use of battlemats and minis. I know that as position markers they boast unequaled precision; used correctly, they can quell or even forestall debates regarding lines of sight, limits of movement, and exposure to the enemy. However I also find (*because* I use them only sparingly?) that they turn a D&D combat into something resembling a chess game, whereas I'd prefer to picture in my mind a Jackie Chan movie or the fencing scenes in "The Princess Bride," or something along those lines. I find myself focusing on whether *this* miniature can reach *that* square, rather than how darn intimidating it must be to watch the ogre mage fighter/duelist enter the room.
Another trouble I have with miniatures is the "suspension of disbelief" factor. In games where I've used miniatures, I've invariably had to mix (terrific

) painted minis, dice, Legos, scraps of paper, coins, and/or whatever else is laying around... because I have quite a few PC minis but nearly no beasties. Personally, I find a marker-lined battlemat strewn with such things looks a little strange to me, and I also find it a lot of work to extrapolate from such a mishmash to a "movie scene" or what have you.
I don't have a problem with D&D3.1 (I really think 3.5 is a misnomer, but I'm sure I've already lost that one

) clarifying and tightening up the rules for using miniatures with the combat system; in fact, I imagine it'll be a Good Thing(tm) all round. I'm a little fearful that the updated rules will make it quite inconvenient to *not* use miniatures as I usually choose to do, but of course realistically all I can do is wait and see. I certainly hope it'll continue to be just as easy to keep the battlefield in my head and conduct combats in narrative fashion as I'm accustomed to doing.
YMMV.