I haven't had a chance to try out the TC yet, need to buy some different coils. As for the vape being different each time, I haven't really noticed that. For the last two years I have been using a mech with a Evolv Kick 2 and the DC output is definitely smoother, but not that big a deal. The button hasn't been an issues for me either. All and all, for 34 bucks, with tank included, I'm pretty impressed. Same goes for my wife's joyetech VTC mini, which is pretty much the same device. I think they both offer a lot for the money.
Indeed they are a great value, I own 4 of them. But the new DNA75 chip is a step up in performance. Nothing quite as small as a Pico, but the SMY SDNA75, is the same size as a VTC Mini, and can be found for about $60-65. The new HCigar VT75 Nano is also very small, but there are some issues with the battery cover, search on ECF and you will find threads for both of those devices if you are interested in trying a DNA VAPE!