I too am finding the sync part on the iphone app very slow when I have been busy all day in OF on the mac.
Just took about 2-3 minutes with the sync progress bar on the screen.
I only modified about 20 items today in OF on the mac.
For now I am having to disable autosync in the preferences and then run it manually when I want it.
Otherwise as other mentioned when I quickly jump on it to add an item it hangs on the sync.
Please speed it up.

Russ