Yes.
Mostly problem-free here. I'll always have the typical hiccups like anything found in smartphones or computers. Problems comes with the territory for almost anything nowadays.
But for my next phone, it may not be an iPhone this time. I may try something different. Maybe an Android, or if Nokia can battle Nintendo 3D gaming, maybe I will go back to them and their Meego. I can always get next year's iPod touch to be close to the "experience" of the iPhone and probably get the 128GB storage I wouldn't mind having right now. This iPhone 4 is already my third device with iOS that I've owned, so maybe I could just end my iPhone ownership in grand-style with a happy experience. I just don't see iPhone changing that much in a few years, and even if it did, will it really be better? Every company can runs its course with innovation. Look at Sony with the PlayStation brand. The "cool factor" will wear off eventually. In cell phones, things become popular like a fad. Right now, people love the OS of iPhone, but remember when flip phones were still trendy and hardly anyone really carries them now? Back then, it wasn't the OS but being thin.
I will probably get bored of those other OSes too and will probably go back to iPhone eventually. But just like my women, I like variety.