I have a grace frame with a Juki 98QT. I love them! I bought the frame off craigs list. It had hardly been used. The lady was unable to use it due to her health. It came mostly assembled. We just took it apart enough to get it in the van to take it home.
I was using a Bernina 850 Record (about 35+ years old) with it but was concerned about burning up the motor so Santa brought me a Juki 98QT. Great machine! It sews very fast!!! I have just made a few quilts so my quilting is free motion. I haven't tried to follow a pattern yet. I just turn on some good music and "go with the flow". Very fun!
My favorite feature on the Juki is the thread cutting button. (not all models have it) I think it is worth it!
One draw back-it can be a bit tricky getting the bobbin in. It is a little space and if you have big hands it might be a problem.
My grace frame is set up for king and it will stay that way. It isn't easy to change back and forth. It takes a lot of room, so consider that when planning out your space. I have storage bins under it and rolly carts with fabric and notions. Works well for me.