Chicago does make you portable anywhere.
It doesn't make you as portable as Harvard, Yale, or Stanford. You close those doors by doing ED at Chicago.
Also, speaking from experience, the clerkship opportunities for transfers in to Chicago are surprisingly low; at least if the various advisors are to be believed.
You're sniping at someone who transferred in to the school via ED. I got 2 callbacks, 1 offer via OCI, despite being on a secondary journal (at the time of OCI, I was the only transfer on a journal of any kind.) I'm well over the GPA for "Highest Honors"--a line that is only given once every few years--yet I'm being told that my CoA--and even district courts in Chicago/Wisconsin--possibilities are quite bleak, even though I have an ed board position on my secondary.
The reason I say only ED at Chicago if you're sure you want to practice in Chicago is because you really *don't* lose much Chicago cachet by closing off HYS if you jump on Chicago--and the life certainty that is supplied by knowing in May, instead of August--and the ability that gives you to focus on the write-on and such, is significant.
Do you folks want to stop being holier-than-thou because you read some stuff, now? Fuck's sake. Chicago is a great school, but make no mistake, you give up some stuff by closing the HYS door.