I have both a full size Grace quilting machine and the Janome 1600. I've had good luck with both. I haven't gotten to a full size quilt yet cause I'm still practicing with lap robes etc.
Yes, you do not have the same space to quilt on as a deep throat long arm machine but you also don't have to pay the high price.
It takes me a little longer to quilt and I have to figure out my patterns but I love the setup. I tried hand quilting and that's not for me. Also tried quilting on my machine with no frame. That was hard work and no fun wrestling a king size quilt under the throat or over my shoulder. I even tried Flynn's quilter and tho that was better, it still wasn't the answer. I'm in no special hurry and one thing I have at my age is time.