No, it's not the same. EDGE stays on. You just won't slip onto some other non-unlimited roaming EDGE service you get billed by the kilobyte or something. Like you're from Cleveland but checking e-mail over WiFi from a cafe in Lyon, but there's EDGE around and the iPhone thinks the EDGE is stronger signal, so roams over to it and you get a $100 whack on your bill for that photo of your youngest child picking his nose with a pencil.
If you are on ATT (or other, like EU, partner carrier in future) you have EDGE unlimited data plan, turning EDGE roaming off is all you need. If it won't roam, you have no fear of extra charges. If people want to turn EDGE off period so they won't accidentally access EDGE services with unlocked voice-service-only iPhones, I wouldn't expect Apple to provide that feature for you -- I think they'd be okay with you getting smacked with a $4,500 data bill.
so ur saying that turning off edge roaming wont do anything if we have an iphone with no data plan on att.