Being old fashioned and throwing some oil in a 3-qt pot and popping it on the stove, we always ended up with quite a bit of unpopped kernels and had a few times with some burned popcorn.  Although we have only used it a few times, we have been very impressed.  

I am not saying it was the machine, but we were pleasantly surprised that using some popcorn that was more than 6 months old every single kernel popped.  I had never experienced that. 

So easy to use and easy to clean.

The only problem we experienced was eating too much.