Not "right back", but I did return. And my leaving iPhone in the first place was not really a choice but a necessity.
I had the 3G, which was an AT&T exclusive. Less than a year later, AT&T service in my area had degraded to the point I could not even successfully call 911 (I tried...) so I had to switch carriers.
On Verizon, I had a WinMobile 6.5 phone for about 36 hours, then the Blackberry Storm 2. I went through SEVEN of those in less than 16 months (one replacement arrived dead) before I could convince VZW it was a piece of crap and get an early upgrade. iPhone was not yet on VZW, so I got an Android, the original Moto Droid X, running Gingerbread (2.2). Had that for about 2 1/2 years, then my next phone was the iPhone 5.
One thing brought me back to the iPhone: Media Management. I had spent the prior four years looking for something that would work like iTunes with anything like iTunes does with the iPhone. I absolutely rely on the live updating smart playlists and two-way sync in order to manage the music on my device.