I started with a Bell & Howell FD35 (Canon TX) with no grip. Moved up to the Canon AE-1, which had this small piece of plastic that resembles a grip. Then I moved to the Canon EOS 620, which has a nice thick grip. 25 years later, I bought a Rebet XT. My hands are not big, but the XT didn't feel great in my hands, so I got a grip. The added batteries and weight (IMO) made it feel much more comfortable. On Friday, I got a 50D. A considerably larger body. Where you hold it feels good, but honestly, my pinky can't find a home on it. I spent the last 2 days contemplating a grip for it. It also seems that the battery life on the 50D isn't very good with a single battery, and, I really dislike neck straps. So, a new BG is on it's way from Adorama.
I think that you'll find the camera will feel a little more comfortable when you have he grip. It's all about that pinky. The grip doesn't thicken the area where you grab the body, it just gives your pinky a home, but it makes a difference.
I never had a battery drain problem with the gripped XT, except one time when I shot nearly 2,000 shots during a group modeling event, but it sure was nice not worrying about it. True, a battery change takes all of 30 seconds, but it could be a critical 30 seconds that you don't want to miss.
I'll lay 2:1 odds you end up liking and keeping the grip on a Rebel.