The closer the mini looks, the better
I have the exact opposite point of view. The less the place-holders look like actual creatures the better. Typically, PCs are matchsticks coloured in with a felt-tip pen (I think in the US they're called 'sharpies') and jammed in a blob of blu-tack.
If you start down the route of trying to use miniatures that look like what they're meant to be, you find yourself adapting your character to what they look like, getting confused about discrepancies ("wait - is this gnoll an orc or a hobgoblin?") and shaping encounters around what miniatures you have ("why are we fighting a lich and three angels again?").
Description shouldn't be influenced by the miniature because you're less free to describe things how you like. Encounters shouldn't be limited by miniatures because you're less free to create what you want. If I suddenly decide to throw my players into a pit with a pit fiend (where else would one be?) and his twenty legion devil lackeys, I don't want to be worrying about how I'll represent them or where I'll get the miniatures. And I don't want to swap him for a Glabrezu just because I have the miniature.
You can ignore the miniatures, but if you try to ignore in some places and represent in others, then you're inconsistent and people will have to keep asking what is what. Get bits of paper or sawn off bits of dowel or painted pennies or something, with r1, r2 and g1 written on them - voilá! You have two Reavers and a Ghoul and your players will remember what each is and which they've hit. And when I tell them the Reavers are translucent, spectral figures with long pale hair that floats ethereally about them, then that's what the players are going to see!
It's like the "Uncanny Valley" for those familiar with the concept. If you can't get what you want, then close to what you want is more disconcerting than something that clearly and definitely isn't what you want.
Ooops, sorry. Ranted.
