I posted on a previous thread about slow backups that my Ipad with around 48GB of apps, music, films etc, took around 11 minutes to backup.
Then suddenly a couple of days ago after about 5 hours I cancelled the backup as it was only about half way through.
I worked out what had changed and it seems a rather strange phenomena similar to the reported wifi problem that appears to respond to turning off the auto screen brightness.
I don't like to turn the volume up too high when listening to music through ear buds as I value my hearing. This means that the base is generally lacking, so I went into the iPod settings and set the equaliser for base boost. Suddenly, the backup was just too slow to bear.
Some time back I had a problem with slow backup with my iPhone and resolved the issue by deleting the backup in iTunes (go to preferences > devices > backup) and doing a brand new backup rather than incremental. I did this with the iPad backup and left the iPad connected to my Macbook Pro overnight. It took six hours to backup from scratch but tonight I've done a sync and backup and it's back to around ten minutes.
I hope this helps some people.