It seems from what intel I have gathered from the Apple store reps that there will be two ways of using a dock.
a) Buy the iPhone 4 custom dock (nothing else works) $29
b) Use a universal dock $49 (buy the $9 insert)
I think both of these ideas sucks, but obviously $9 sucks a lot less than $29
I have yet to test to see if the iPhone 3G dock will work - it may just because the back area is so much thinner on the iPhone 4 - but there would likely be a high chance of it falling off due to a lack of support.
a) Buy the iPhone 4 custom dock (nothing else works) $29
b) Use a universal dock $49 (buy the $9 insert)
I think both of these ideas sucks, but obviously $9 sucks a lot less than $29
I have yet to test to see if the iPhone 3G dock will work - it may just because the back area is so much thinner on the iPhone 4 - but there would likely be a high chance of it falling off due to a lack of support.