IPhone's record at 1920 x 1080 only and records at 30fps which is where it differs from GoPro which of course can record at far higher frame rates, but this only really has effect for the super slo-mo videos of your friends crashing
I see Jons point about suport for other makes, this applies to nearly everything though as there are millions of apps and accessories that are for the iPhone only,that is the main reason I choose one (its not my fave phone but there are just so many great accessories like the Product-X) availble that its hard to resist.
An adjustable one would be great but I imagine hard to create especially as most camera lenses are in different positions.
Ive just moved mine slightly on the backpack as whilst the videos above are good, I found when I was standing the angle changed and it filmed too much of the bike, its been moved slightly upwards so Ill give it a go later.
Andy