I love the idt because you can use the 1/4" foot with it for putting binding on. As long as the foot has an opening at the back to accomodate the idt lever, you can use any foot with it. If you use the info feature,the lcd display tells you what foot to use and whether you can use idt with a particular stitch.
I use the idt all the time even when piecing.
I am a pfaffaholic!!!