There's definitely something to be said of charging one's phone 80-100%. I notice (using a Kill-a-Watt) that the phone draws much less than it could past 80% - and trickle charges down to single watts after 95%.
For people using the 5w iPhone charger because they feel that slow charging helps their phone - then only using 80-100% is in their best interest because below 80%, the phone will ask for all the wattage it can if it can get it.
I'm a fairly light user and all my iPhones have faired pretty well within a 2 year lifespan mostly because I've done the 80-100%. This year's iPhone I am doing the 60-80% and notice that the phone gets a little warm when charging due to it not being at 80%+. But so far health remains. From my own personal observations with coconutBattery, doing 80-100% and 60-80% seems almost no difference, at least within a year of ownership.
For those worried about their capacity dropping - I've had batteries come 96% of design capacity from the factory while others, 108%. It's best not to worry too much. Initial battery capacity, lifespan, and longevity seem to me to be so varied that going out of your way to inconvenience yourself to baby these batteries does not seem worth one's time. We read it here on Macrumors - some people wireless charge, drain to 0%, use their phones heavily and are at 100%. Others baby their phones and are at 89%.
I've always gotten the same phone as my wife - so I've gotten to compare a heavy user to me (light user). Even within a 2 year timeframe, our capacities were not terribly different (within a few % points) despite my wife having hundreds of more charge cycles and using her phone very heavily.
I'm still doing the 60-80% because it doesn't inconvenience me all that much (especially working at home). But whenever I go out for a vacation or work trip, I usually will charge to 100% because I rely on my iPhone for communication, airplane tickets, and $.