I have the same system you are looking at and I love it. Yes, to Mytwopals' point there throat space CAN be a bit limited as I found on the quilt I am currently making, however it is the first time in over 3 dozen quilts I have any any problems. I just picked a pattern a bit too large for an extra long quilt. The problem can be resolved by taking the quilt off the frame an turning it around.
If you are making any large size (double, queen or king) quilts you'll recover your investment in no time when compared to the price of having the quilting finished by a professional. Depending on your pattern you stich you can complete a queen sized quilt in a day.
I love my Pfaff Grand Quilter and frame. I can't wait to get my tops pieced so I can start quilting!