Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Good in principle but...

Saw a similar if not identical video on a recent airline flight and it was very impressive. Based on the after-viewing credits scrolling by on the screen, I searched on the web and tracked down this item. The price was great.Unfortunately, the product has not worked on any of the 5 DVD players we've tried it on. Guessing it is a format incompatibility with a US standard. Not sure why this should be the case as our electronics are of fairly recent vintage. We cannot recommend a purchase under these conditions.