Battery Grip is something that you really need to feel for yourself, feel what the added weight is like on the camera and if it is worth the cost. You also may want to check and see if adding the battery grip will allow you to increase you shooting Fps.
The pros probably outweigh the cons when it comes to the question of whether you should use or not use a battery grip.
I can't use my XTi without the battery grip and I have small hands. The camera just feels better balanced and the extra shooting time is a big plus. I used to get roughly 650 shots with a single battery and no grip...now I can shoot over 1300 shots before I have to change batteries.
When I finally do upgrade to a better body (50D, 60D or 5D MkII) I'm definitely going to get a battery grip at the same time plus extra batteries.
I never bothered to get one. When I shooting and go to portrait orientation the right side of the camera goes down and my finger never leaves the shutter release. I don't understand people who have to "twist around" to do this.
My camera doesn't live in a bag. It goes around my neck and I don't need more weight.
It takes me about ten seconds to switch to a new battery in my K10D and I always have a charged battery with me.
If it feels good and you like it or if it looks good and you like it, that's fine. Functionally, it adds nothing for me.