If you remember how disappointed people were when they got their 3S and the 4 came out, I'd stick it out and wait for the 5. It'll probably blow the 4S out of the water just like the 4 did to the 3S.
This is wrong. There has been an iPhone 3g and iPhone 3gs, not an iPhone 3s. As for my opinion on my iPhone 4s, I have had Sprint and this is the first time an iPhone was available for me, so instantly I bought the iPhone 4s.
I personally think it's great, but if you have the iPhone 4 I wouldn't recommend upgrading. Now if you have anything lower than an iPhone 4 than I would recommend upgrading as well because the iOS 5 runs smoother on the iPhone 4 and up.
About Androids, I have had one, and they are a dime a dozen. Yes some may have the same specs, design, camera, etc, but they come out with MULTIPLE Androids every year ATTEMPTING to compete with Apple. Apple only comes out with ONE new phone every year to year and a half, and maybe the iPhone 5 will come out in 2 years. You never know with Apple, they always keep you on your toes.
I had a Blackberry Tour 9630 before I upgraded to my iPhone 4s 16g and once I bought this when my contract renewed for $200, I NEVER looked back.