Have used this about a half-dozen times in the month I had it.  As long as you follow the directions (don't over- or under-fill) you will have very satisfactory results.  Very few un-popped kernels and NO burned popcorn.  Cleanup is quick, with most parts dishwasher safe.  Results are far superior to any microwave or stovetop methods.
Overall, I am very pleased with this purchase, and would recommend it to anyone looking for a better way to make popcorn.