I think the second time around is actually much better. You're more knowledgeable, more committed, and more awake as to the possibilities. Your industry experience also will help.

So in sum, it is definitely NOT harder to get in after a few years working. In my program at the University of Chicago, the only students fully funded were those with at least 4 years out of college (thankfully, including me). Other students were enrolled, but with much smaller funding. Just anecdotal information, to be sure, but not out of the ordinary, I think.

So people are entering school in their late 20s? That sounds right, as I am finding it very hard to get into a PhD program straight from college. I plan to work 3 years save up money and prepare (take GREs over, get better recommendations, read a lot of literature in my field, find out about differnet people and programs to apply to, and craft a very nice personal statement) and then apply again. Does that sound like a better plan?

I wouldn't say that's the case all around. There's a lot to be said for maturity, but also a lot to be said for enthusiasm, pure youthful genius and insouciance. The latter may be even more important in the sciences than in the humanities, but I'd hate to make any blanket statements one way or the other.

Go to graduate school when YOU'RE ready to go. You're personal preparedness for them is much more important than their preparedness for you!