Given reviews from Amazon, classify those review based on their content into two classes: Negative or Positive.

I have been very unhappy with this product because it:1) makes a high pitched buzz2) intermittently stops providing enough power causing my computer to constantly switch back and forth between battery and wall power.3) the cord is difficult to wrapI'll be trying to return it through the warranty process, but I wish I had just coughed up the [lots of] extra money to buy an Apple one.
Negative