Turn your 3G off in your iPhone Settings. Voila, you'll instantly have 5/full bars if you didn't before. If you live/are in an area with poor 3G reception, you'll drop calls like it's cool. The minute you turn off 3G and go back to EDGE only, your phone will work great. That's what I do when I'm home. I have wifi at home so not having 3G is no problem if i need to use internet on my phone, which I rarely do, since I have computers at home.
Apple needs to come up with a better way of automatically switching to EDGE when there is a poor/no 3G coverage.