I found the best way to improve battery life is to turn off GPS and 3G. Both suck data all the time and use battery power to do it. Once they are shut off the battery easily goes all day +. Also make sure stuff like Dropbox is set to only send photos in WiFi.
As for WiFi, I have no problem with mine. It is set to alert me when an open network is available and does all the time. I normally connect with no problem and if its a remembered location it connects automatically.
Sounds like you have a bad unit.