yeah, the only decent data plan Rogers has to offer that would work well would be the $65 dollar data plan that gives you 1GB, and that should be more than enough with EDGE's speed. I don;t think you should even bother.
I jsut grabbed my iphone 2 weeks ago down in Novi, then I went to rogers and got myself a my5 25 plan with some long distance minutes and the $11 value pack. If you don;t need your email and maps 24/7 there's no point, 80% of the time I am in locations with wifi. If you are concerned with maps, there is even a program that lets you use it offline. If you make a new rogers contract, you'll probably get a free phone, i did, beats paying $40 for a sim, plus i sold the phone for $75.
If you are really concerned with data, wait till July or June and get the 3G phone, from what I've read it seems that EDGE is dreadfully slow.
Also, if you don;t want to use EDGE, make sure to call Rogers and disable EDGE on the sim, just in case the iPhone decides it wants to surf the net.