This comment makes a lot of sense..
LOL, j/k
The entire concept behind Push as an alternative to Background processes, is based on BATTERY life. Push, is also already a part of the iPhone, and for those who use it all day long, will tell you yes it uses battery, no more so then checking you email manually. Most of us use email on the iphone in place of SMS with other people who can do the same, so its a constant. Battery isn't great no matter what you do, its a non issue.