Well I have my iPhone 4S, but in the past 12 months or such I've had a
Blackberry Torch 9860, Bold 9900, HTC Sensation, HTC Sensation XE, Samsung Galaxy S2, Nokia N9, Nokia Lumia 800, Samsung Galaxy Nexus and finally a HTC One X
In regards to
Call quality & Reception - best of the bunch was the bold 9900 without a shadow of doubt.
Social features & integration to OS Nokia N9, followed behind by the Lumia 800.
Problems with battery life All the android handsets I've had never seem to last generally 12 hours, or will at least have unpredictable battery life. Once I got 24 hours on my Sensation XE, the next day not using it - it lasted only 9 ? No rhyme or reason.
Best Camera HTC One X - best camera other than the iPhone 4S
Most dissapointing camera N9 & Lumia 800 - because nokia have a reputation for good camera's and this is a Carl Zeis lens, and yet photo's were generally poor. Worse than the BB Bold 9900.
Most bugs before I got rid of it the BB Torch 9860 and the Galaxy Nexus for different reasons. The Galaxy nexus was unusable for calls for the first month due to the 2G volume issues. Made the phone pretty much redundant for me.
If I was to pick just one phone from all the ones I've had - other than the iPhone 4S - it would be the HTC One X