They all seem like a perfect bargain when you start thinking of how much time and effort you'd have to spend to actually MAKE the same part from a piece of sheetmetal. I've spent more than my fair share of money and time replacing cab panels and I'd have to say that overall the quality is good. Most are better and some are worse (inner-to-outer cowls) but all are usable if you have a working knowledge of sheetmetal.
It's been my observation that guys with mechanical skills dismiss sheetmetal as something not requiring any special skills and quickly find themselves in trouble that is, of course, the result of "crappy Chinese parts". Sheetmetal requires a unique set of work skills so if you've never done it before expect to have problems. If you have experience with sheetmetal I think you'll find them to be an overall good value.