I prefer to get a response, regardless of the type of post, because I don't like to think I am being ignored. My witty and insightful review of your fic or comment on your meta obviously deserves acknowledgement!

That said, I'm not too concerned when that reply comes, especially on meta posts, where thoughts can be long and meaty, and it might take a while to formulate a reply. But when I'm reading fic, for example, and I find one that's more than a week old or so and I see that the author hasn't replied to any comments? I won't waste my time commenting, then, if it appears the author doesn't care.