I generally go out every morning with the tongs and grab the poop out of mine. Occasionally if I sleep in a little late, by the time I get in there, they already scratched and scuffled around and its buried under the pine shavings.
From what I have seen with my flock, as long as it's not stinky, or anything nasty like moldy or wet it's not that big of a problem. Another thing to keep an eye out for is pests. If there are a lot of flies or rodents that could be come an issue too.
I only have 4 chickens so it's not that big of a deal in my case thankfully, but with that another thing you can do it you wish, about once a week or so, go in there and just turn the hay over, you don't need to dig all the way to the bottom if you have an open bottom pen, but give it a little turning. Generally any turds that they turned over will dry our fairly fast, and now you have the little dried poops you can pick up or however you collect them, pick em out of the straw and discard.
There is also some powder I seen in the TSC that is like some sort of composting stuff they say to sprinkle on the floor when you put new hay in. Does not seem to to much IMO but another option to look into maybe?
Aaron