I'd much prefer to pay for a game outright. If I can't do that, I usually won't bother with it. I don't mind premium content in games where you can buy the content and that's the end of it. I just look at that as an expansion or DLC. Paying real money for expendable items in a game (Potions, currency, scrolls, etc.) isn't going to happen for me, though.
Probably the most hilarious example of what I'm talking about is some of the multiplayer flash games. Where a third of your screen is taken up by buttons trying to get you to buy the in game currency, and you aren't going to advance without doing it. Killing a foo gives a dollar, and the cheapest weapon in the shop is a hundred thousand bucks sort of thing. The second I see any multiplayer game has ridiculous amounts of game balance shifting stuff for sale, I'm done with it entirely. Though when I played I didn't mind EQ's, because the vast majority of the stuff you could buy for real money was cosmetic or easily obtainable in the game, which is a different matter entirely.