I have a leather case on my SG4 and before this one, I had a gel back. I have dropped it numerous times with no dents etc. I also tripped on a paving stone and my phone went flying about 30feet into the road. Luckily another pedestrian picked it up before a car ran over it...
I would not trust the phone on it's own to not ding, dent or scratch. Spend $8 and get a good cover. It's the best investment for a ?800 phone.