I have, I work at a teaching hospital that offers a discount. I just show up with my work id, and get the computer at a reduced rate.
The Employee purchase plan is a bit different, you need to buy it through a separate site, you cannot just walk in. My wife can do this, with her organization but my edu discount is usually good enough we've never really done EPP
I used the educational discount online after visiting an Apple store and talking to an Apple guy about a rMBP. He advised me on the configuration, and it was midrange... He said, well you need to order this online, and you have a kid in college, right, wink, wink? I mean, he really did that! He practically asked me to take the discount. Nice guy. Still have to wait 3-4 weeks for shipment, but oh well.