I like it. But I can't free motion quilt for the life of me so I admire your talent. I think it looks good!
As for the build up. For me it would depend on how it looked after being washed because of crinkling it may hide a majority of the build up. However. It doesn't look bad. I don't think it looks like one mass of knots or that it looks bad at all. Fwiw I would buy a quilt that looked like that.