Normally its hard for iphone users to do a maunal disable of automatic update in itunes. Backoff  a free iphone app  and Mac app that allows speed synchronization of the iPhone disabling the automatic backup in iTunes.

  1. BackOff is free.
  2. One Click to Turn Off / On.
  3. PC Windows (XP, Vista, 7) & Mac OSX (Tiger, Leopard, Snow Leopard) compatibility.
  4. Supports iPhone V1, 3G, 3G S & iPod Touch V1, V2 and V3.
  5. Supports iTunes 9.0.2

When the automatic backup feature is active in itunes  and archived data are many, it is possible that the timing is rather slow. Using Iphone backoff application you can disable and enable the functionality in a simple way, starting Backoff you can check whether the automatic backups are active and shows a button through which change the state.

When the feature is disabled is not done a backup of data on the iPhone so you have to use this tool carefully.