IDT was the reason I bought my pfaff as well. I love it! It makes a huge difference, to the point where even though I'm not the most aware person, I notice straight away when I've left it off and start straight stitching.
The only con I have is that I could've bought a janome without IDT for the same price or cheaper with more features (such as thread snips, knee lift etc, I have the quilt expression 2.0) but I'd say it's well worth the price.