anyone below 700 accepted at Chicago?

Well, actually I don't think the simple answer is "700 or 730 is not enough". People will undoubtadly get in with lower scores, but I believe the truth is that it is extremely difficult to distinguish yourself through essays. The statement that you see all the time, which I find really naive, is "you scored XXX which puts you in range, now just go and write some awesome essays!" Essays are similar to the GMAT in that some people will inherently be more capable, and others will not be able to produce top-notch results no matter how hard they work at it. We don't believe that everyone can score in the 90th, 95th or 99th percentile on the GMAT; we also shouldn't believe that everyone can produce elite level essays.

Distinguishing yourself through stellar essays is made even more difficult because 1) each person is limited by material from their own past, and 2) there's no guarantee that whoever reads your essay will find it to be a masterpiece, even if it is one. Let's look at these two points for a second.

Point #1: Some people have interesting things in their past to talk about, and some people don't. Even if you are the best essay writer in the world, you can't make a silk purse out of a sows ear. The best applicants will be talking about club leadership experiences at top universities, excellent work experiences with big name firms and extracurriculars activities and community service that will knock your socks off. If you don't have these things in your background, all the hard work in the world will not make them magically appear in your background and there's just nothing you can do about it within a few months.

Point #2: As has been discussed before, you have no idea who will read your essays. If the person is tired, or bored, or doesn't like your writing style, that's just tough luck. The same goes for recommendations and interviews - it's just ridiculous to assume that yours will be among the very best given all the variables involved. As far as work experience, unless you have something that is truly distinguishing or well known, one person's puffery will sound just like the 30 others that the reader will see that day.

On the other hand, 50 points more on the GMAT is right there in black and white. Even if it takes a lot of hard work, if you can improve by 30 or 50 or more points, I would say that it is worth the effort. I have never suggested that people concentrate on the GMAT at the expense of other aspects of the application; but I think it is a poor assumption that people will produce substantially better essays if they have more time to work on them. I have been involved with academic and professional writing at many levels, and I definitely believe that most people will not continue to improve their essays after a given amount of work has been put in. Certainly you need to put in the hours of self-reflection, and drafting and re-writing; but at some point another 50-100 hours of work is not going to result in an improved product. If another 50-100 hours of work will improve your GMAT by 50 points, then that is a hard result you can carry with you. The GMAT is the only thing you really have full control over at this point.