I just bought 3 4s about 3 weeks ago and have had very few problems. I'll list just a few pros and cons.
-huge assortment of apps, but apart from what you'll hear from certain folks, some do crash time to time. I've had issues mostly with certain readers and productivity apps such as business card scanners.
-very seamless experience between itunes and the phones, wireless syncing, streaming music, configurable through itunes on my laptop and sync to phone.
-icloud works flawlessly so far, although the 5Gb free limit may not be enough for some users, the free email is nice.
-facetime, messaging, Siri all do their jobs well, although any background noise can throw the voice recognition off if you don't speak very slowly and clearly.
-Battery life is my biggest complaint. I would love to use this for a full day without having to plug it in, but I usually get the 20% warning well before dinner time rolls around.
-Screen and visual quality is excellent, the camera and various apps for photography all do an outstanding job for general photo taking.
That's all that comes to mind at the moment. I love the phone, ios is sweet and I will probably stay with it for some time.
The only real comparison I can make is with my supervisor's galaxy, not sure of the exact model, but it's a new release and he certainly isn't as enamored with his as I am with my phone. I use the heck out of this thing...