Bf just got the S3 and he loves it but it's because he had a crappy blackberry before. I've used it a little, it's pretty fast, resolution is really good, its definitely better than my iphone 4 but I havent tried the 5. I had the galaxy s for a while but it was horrible and pretty buggy, way worse than the iphone 3gs(but that might be unfair comparision im not sure).
I like the feel and quality of iphones better than others. But I'm biased because it's the only smartphone I've used and have been using them for over 3 years now. As far as usablility, again I prefer iphone because I'm biased but I've noticed that in some cases androids require an extra step (for example, calling a business from google maps).
I've had a horrible time though trying to back up, restore and transfer data (music, photos, etc) with the iphone. The icloud sucks. I believe it's much easier on the android platform.
From a moral viewpoint I prefer android because apple is so damn proprietary and I am a pc girl. But for superficial reasons and comfort level, I still use apple.