Well, iPhone 4 is now an 8-month old phone. Folks either got it already and sales already saturated with this model or the ones who didn't get it are just waiting for the next one. Even iPhone 4 fell out of the TOP 5 in the UK with the HTC Desire being #1.
iPhone turns 4 this year. Anything in life can get OLD and tiresome.
I am getting bored of all the OSes right now. I played with the Atrix 4G the other day and Android still isn't buttery smooth with its multi-touch like iPhone. I've supported Android since the beginning and now feel it is just the ugly twin sister of iOS with more steps to get done. I got a better experience from WP7 and even I know the lack of customizing it will make it boring after awhile. I want XPERIA PLAY, but Android is becoming such a turn-off for me and who knows if the OEM updates them responsibly compared to the Nexus phones. I heard the Motorola XOOM's Honeycomb software is still buggy.
The only OS that interest me is QNX. Ironically, QNX has been around a lot longer than people realize. That looks like it is optimized for multi-cores. But knowing RIM, it could take awhile before we start seeing them in phones and not just tablets. It still takes years to catch up to apps and refinement with the hardware and battery life. I'm sticking with iPhone for awhile since iTunes cards are accessible and doesn't need a credit card to pay for apps like I do with Android. But at the same time, iPhone is getting rather boring and I don't want to use Apple forever since I don't necessarily like them either. I do want to try something else, but I haven't found the one phone where I can truly love the software, hardware, and the company that produces it.