Once every few weeks with a 3GS.
6 over the weekend with the iP4. I probably made about 25-30 calls, so roughly 20%. First call I made with the phone dropped - in my house, where I plan on using it quite frequently.
I'm going to wait for this 'magical' software update, but I don't expect anything out of it beyond making it look like I have 5 bars everywhere (like they did with the 3G and 3GS), and then they can blame AT&T.