Depends on how you use the device. I doubt that you would notice any difference in email send and receive. Email can't send/receive in EDGE while you are on a call however.
You might notice a slight difference in browsing speed, but only slight. You would see a faster connection if you tether.
Battery life should be better in EDGE as you aren't constantly searching for a 3G signal.
Might be a couple other concerns that I didn't think about.