Hmm. I've had two giantomizers so far, one was the older model type, had one refill hole and the mouthpiece also acted as the plug for it. That was, to put it mildly really quite annoying to use. Leaking window, burnt taste, plastic taste, wicking issues... Rubbish.
Was advised the V2 versions were much better, found a uk vendor doing them and tried it. It was much, much better, but still a little lacking from what I'm used to (CE2 XL's and cartomizers mainly). Vapour production was pretty poor, though flavour was quite good. It also had a really loose mouthpiece which I never felt secure about, worrying it would leak like crazy in my pocket. it sits left alone in my vast
vaping gear draws, unlikely I'll get it out again anytime soon.
A mixed bag in my experience then, I may have just been unlucky though.