I was in the same position. iPhone 3 was my first smart phone and I'd upgraded to each new iPhone the day they were released.
HTC One X was my first Android and there is simply no going back now. This phone in particular seemed to ease my transition with Sense which adds just that bit of polish to the UI that those of us used to having our experience "heavily managed" by Apple find somewhat comforting. When you add in the brilliance of the device size and functionality itself, well, there's just no comparison.
Until recently selling my iPhone 4, I would occasionally access the phone for something and was immediately struck by how shockingly tiny the phone seemed after quickly getting used to the added real estate of the HTC One X screen. It felt like my finger overwhelmed the screen -- really weird sensation.
The somewhat skimpy storage space hasn't been an issue for me. I utilize Google Play and the likes and just realized yesterday that it quietly caches the music I listen to when connected so it's available when I'm in a bad connection area even though I haven't explicitly synced that music to my phone. My storage still shows over 50% of space still available.
I was concerned about my data usage (even though I'm still gripping tightly onto my AT&T unlimited data plan) and I was really surprised to see my data usage has only increased by about 20% -- I'm still significantly under what AT&T allows on their least expensive plan. I do have Wi-Fi at home and at work, but commute by bus 5 days a week and regularly use my phone for reading, surfing, etc... although I don't tend to stream video when not connected.
I did find the app switching issue really annoying. The second you minimized an app it had to reload when you brought it up again, even if you went right back to that one. But the latest release has made that better and app updates themselves seem to be finding ways to mask the problem too.
So, as one previously devoted iFan, I have zero regrets and find myself enjoying my phone again in a way I did in the early iPhone days. I love the flexibility I have in the Android OS -- and although I'll never root my device, the flexibility is still amazing in comparison.