Photojazz,
I looked at getting the s5 recently because of the quality of the images that I saw on various sites e.g
http://www.dpreview.com
In addition to the site suggested by Jiminy, dpreview also has a detailed review of both the s3 & s5 which may assist you in making your decision.
I personally could not justify myself paying a few hundred dollars more compared to other brands with more features. I would however have bought it at the right price.
Cheers