For me? No. I had 15 hours of normal use yesterday (moderate user), and I was down to 53%. My iphone 4 would have been dead. I WILL pick up an extra regular battery eventually, but thats just in case, or when on vacation and using it A LOT.
Your needs may be completely different. And if you use the phone A LOT, then it might be great for you. I am a fan of sticking with Samsung/verizon branded batteries, whether extended or regular sized.