I doubt you'd find any love for Duncan from any TPM commenter.
Yep. Staff a school cheaply by giving crappy benefits, siphon off the least-costly students from the public schools, let the public schools handle variation in student population while you can admit for 100% space utilization year after year, invest in (or rent) only enough physical plant to impress parents rather than to fully address education needs, make good bucks if your marketing is effective enough, and close down with little warning and dump the kids back in the public system if you don't get the numbers.
Innovation in education is a good thing, and charter schools have helped to motivate districts to work a little harder and faster at it. However, that's been an unintended byproduct in most cases. Most often, charter schools have been enabled by and operated by people who want to weaken or eliminate the public option.