Good review, thank you. I have one of these and... voltage changes between 3.0 and 4.0 ish have little effect, which is a failing of most PWM devices. Above this, change is noticeable and immediate so maybe you had a defective unit? This wouldn't surprise me. I wrote to Cig Star via their web site enquiring what their warranty was and got no response. So possibly standard craply unreliable Chinese build standard and poor customer focus. Build it, sell it, stuff the customer. I hope I have a 'good 'un' because I like this and above 4.2v the voltage changes seem to be immediate and noticeable and the general build standard (at purchase - will be interested to see what it looks like in a year) is good. I timed the response on the change variables and like the other person reviewing on here, it was 4 seconds too and not the 2 the manufacturer stated.