Description lies. It promises 100% free unlimited but there is a 1000 MB daily limit after which you get banned for 24 hours.
I only used it 2 hours today to watch low quality video (at 1MB speed), and I got blocked. How much data could I've possibly used to get this 24 hr restriction? Earlier I've used it for 4-6 hours with no problems. There should be some kind of indicator to avoid data overuse. Otherwise its a good extension.