I switched to an iPhone. It was pretty quick.
I had handled it as an iPod for roughly a week. Sadly, after just that one week I was convinced that I wanted to ditch my Pre 2 for an iPhone.
Why? The hardware. It's solid, not a single plasticky creaking noise, and best of all, no moving parts.
I hate moving parts on devices. I loved my Treo 680, it had no moving parts. When the Pre came out I made a huge exception because I wasn't too thrilled with non-GSM networks and I hated slider devices.
Now I'm back in GSM land with the jesusPhone.
Some things that I've noticed in my switch, an iOS vs. webOS comparison of sorts, actually no, more like simple observations:
Having said all that, I'm still into webOS. I'm still developing on the Touchpad. I'm just waiting until HP gives me what I really want, a solid candy bar shaped webOS device with a 3.5-3.6 screen.