The great miniatures debate perplexes me. Do I need to use miniatures in my fantasy game? No.
But do I like miniatures because they are super cool and a nifty way to visualize characters and scenes? Yes.
I use miniatures only because they're awesome, not because the players are threatening to revolt if we don't map out every square inch of the battlefield and place our figures accordingly. We spend half our time simply pawing through the piles of figures, finding unnoticed gems in my collection and wondering when they'll make an appearance in the game. Miniatures also serve to plant the seeds for a new character concept. (Example: "Whoa—what do you think that sorcerer is carrying in his backpack?")
I use D&D minis and Mage Knight pieces because they're affordable and because I can throw them in a cardboard box between sessions without having to worry about chipping the paint. Yes, I play wargames and paint miniatures myself. I'm just not particularly inspired to paint minis for roleplaying games, y'know?
The point is, my group uses miniatures not as a crutch, but as a way of enhancing our gaming experience. The system we're using (Savage Worlds) is actually written to accomodate and encourage the use of miniatures, but we've had no problem using the rules as-is without leaning on minis.