I just got cingular with the Blackjack which is a cool phone, but I quickly noticed how horrible the sound quality is especially with the unusuable speaker phone so I'm deciding on going back to a treo(had the 700p with crappy sprint). I still have my 700p with service for a few more days and the sound quality is superior by far so I want the 680 but have heard about horrible battery life though also heard about some software upgrade with the camera.
Battery life is not like the 650. You are getting a smaller battery so expect a shorter battery life. I bought an extra battery for that purpose. The camera updates do help, but also optimize your setting like screen brightness, level of ringer, bluetooth adn infrared off, to make the battery last longer. Also, if you are doing email and web expect to run out of juice by the end of the day. Recharge at night and after a few recharges the battery seems to be getting better. The 700p shouldnt be that much different from the 680, only antenna and battery so it may not be worth it. speakerphone is loud but not amazing, signal and soud quality is amazing. Hope this helps.