Thomas Palley has written (yet another) MMT critique; with comments by Ramanan here. The Mike Norman Economics site has a link, with comments there. I am looking at other things right now, and I only scanned the summary. My feeling is that it revolves around political economy issues that I am not particularly concerned with. (I am currently letting my manuscript rest, will go over it again shortly, and see whether it is worthwhile adding this Palley critique to the list of critiques.)
My current interest is that I am looking at the replication code for the calculation of r* (New York Fed website). Not sure when I will be able to comment on that.