I just bought an S4 2 months ago, and I'm having to sell it and go back to an S3. The wolfson audio chip was a beast for quality, and the S3 is still awesome on battery life and no slouch. I don't really play super intense games that need the latest hardware, so the S5 just doesn't seem that appealing.
I was hopeful that it was going to be completely redesigned and have enough wow to warrant an upgrade, but looks as though Samsung couldn't afford a new drawing board, so they stuck with minimally increasing screen size, adding another useless gimmicky feature, and trying to appeal to the masses with Glam style.
Yes it's now water and dust proof to some degree, and they have boosted the camera somewhat, but I don't think that will be enough to convince people to upgrade from even an S3.
Overall, I know Samsung could have done a lot better. Whoever is making their design decisions needs to be replaced!!