I just got my new battery yesterday. I was hoping to hold out until the SGS3 arrives, but the battery went downhill quick! It started dropping 50% (i.e 80% to 30%) in a matter of minutes. It wasn't worth saving the $4 for a new battery. My old battery was swollen, but it was hardly noticeable looking at it. I could feel the slight bulging when I slid my finger over it though.
Two more weeks until SGS3 time...