I have the Pfaff equivalent of that machine, and I'm thrilled to have it! I don't know about the frame though.
My machine tends to be picky about threads, you may have to experiment to see what works for you. The comment about limited quilting space is a good one, but compared to most DSMs, it's still very generous.
I do know this machine is one of the heavier machines for the short-arm quilting, so the comment about bowing is accurate- I had mine on a New Joy Gold Standard until about 9 months ago, and at the full 10' length I had a lot of bowing. I bought a New Joy Magic frame, and haven't had any issues (but this frame will take an 18" machine, too).
$5485 is a fantastic price for a machine & frame, especially if you're not sure that you're going to like doing frame quilting. And if you don't? That machine is fantastic as a piecing machine or free-motion on a table. The one thing I would ask is if the person had their machine serviced regularly.