This is a danger in the market, and I see it in reviews all the time. Every limitation of the system is the fault of the developer of the app, and the reason the app is slow is because the developer is bad (not because the customer picked a phone with a 700mhz CPU).
The app markets really need a way to protect developers from abusive customers. Amazon lets other customers respond to a review, and Newegg lets the maker of the product respond. Maybe the Android Market needs this, too.