I don't have one of these but I've played with them in shops several times, I've been thinking of getting one for a year or so but haven't quite convinced myself to do it. (Lack of space is a big issue)
I don't like their stitch regulator. It seems clumsy to me, and you have to reposition the sensor thingy all the time or the fabric will move without moving the sensor and that doesn't do any good. So when I've tried using it, I end up with some pretty bad spots that I don't get without it. If I had one at home and practiced a lot more I'm sure I'd get better at it, but it just seems like more hassle than it's worth.
I also have decided to go ahead and be stubborn and just learn how to have better control MYSELF. That way my FMQ abilities will work on any machine, not just one with a regulator. I am still learning, but I do improve with every quilt!
So when I mentally price out these machines, I no longer even consider a stitch regulator.