When I first purchased my iPhone 3gs, I was eyeing Android and thought it would be a good 3 years before the latter was at the place where I was ready to jump ship. Even then, it was not hard to see a number of its advantages.
I liked my 3gs; I eventually upgraded to the iPhone 4 which, for the most part, I also liked. But what eventually started to really gnaw at me were these issues:
1) I don't like how iPhone apps use screen real estate. I didn't initially like the idea of back buttons, etc., but realized they really make viewing much better.
2) I like widgets.
3) I only use 20% of the apps I own frequently; I want to hide the rest so that they don't clutter my UI
4) The camera isn't fast enough
5) I don't like how with every software update, Apple makes "older" phones slower and less usable. iOS 5.1 is a bear on the iPhone 4 and it doesn't need to be. It feels more like Apple is pushing me toward buying the next thing by turning my phone to poop rather than keeping me happy--and this became especially palpable when certain apps stopped working when I chose to delay my download of iOS 5.1.
6) iTunes is clunky, slow, disorganized, and by now personal storage of data is really unnecessary
7) iCloud is underdeveloped, hard to use for most practical purposes--or at least, harder than Drive--unnecessarily parochial and proprietary, and doesn't do much. It's way too far behind Google, Dropbox, etc.
8) In day-to-day life I'm very dependent upon Google cloud services, and Apple and Google both seem to work hard to make the user experiences unpleasant on an iPhone. iCal is pretty, but it's a pain; gCal is more austere, but far more flexible, ubiquitous, and useful.
10) Because Apple is intent on replicating it's own versions of good services that already exist and screwing its competitors to force its customers to use its own, all the while said services are substandard, it makes for a very conflicted and unpleasant user experience.
11) In general, I'm dissatisfied with iOS app fragmentation. I live in NYC; I have 3 different subway apps that do awesome things, but which should be 1 app.
12) I started to want a larger screen.
13) Multitasking is horrific. The Cydia versions are all infinitely better.
None of this is to say I hated my iPhone. I really liked it. I just hated what Apple was doing to it.
Anyway, once ICS was released, I knew the 3 years was up and the time had come. It basically addressed most of the issues I had with the iPhone and Apple's philosophy toward its products, developers, and customers. I played with the Galaxy Nexus; it was ok, but not what I wanted yet, for all the reasons the reviews mentioned--the pentile screen, battery, camera, etc.
I thought I'd wait until the Galaxy S3 came out, but the One X hit first. Frankly, once I saw the reviews, I didn't care. I care even less now that I know what the S3 will be like--which is great, but not enough that I care (save maybe the larger battery).
The One X and ICS seemed amazing. It certainly has its own issues too. I'm definitely NOT thrilled with the alterations to the multitasking, for instance. It's unnecessary and painful to use; the unaltered ICS version was superior. The raised screen also makes me nervous. Makes it feel very vulnerable.
Nevertheless, I'm quite happy. It's been delightful to use.