MF on unique drops made some of the lesser/crappy gear any player could find more valuable (if a high % was found) and thus allowed players to trade up for better gear. So in the end even if you didn't use the MF gear you could trade it to players who did want it and possibly get an item of value in return.
So... how did MF play a negative towards your characters? Because you didn't get the drops you wanted? I had 500%+ MF and I still didn't get the drops I wanted but I got my MF up so that I had a higher chance. I ended up trading for most the items I got but without MF the chances of me getting the drops (that I traded) would be much diminished.
Plus giving everyone the same chance to find items will cause a market saturation at an every increasing rate as more and more players reach the top levels/hardest difficulty.
Blizzcon '09 better discuss and explain this MF topic. Apparently there is a big divide on if it should be in the game or not. I personally believe it should be in the game. Adds another element of depth to the game that would be an additional hook to many players.
Equal chance to find a certain item (as in a percent chance for a boss to drop such-and-such item) feels way to much like an MMO (WoW?) so I say Diablo goes in the direction that was already pre-set in Diablo 2 - Magic Find.