While the already mentioned battery capacity is certainly a con, if only minor, I think the biggest flaw for many is the DNA 30's inability to buck voltage... It's an awesome setup for an RTA. I think I'll spring for one... But many clearos today offer a highest resistance of 1.5Ω. That's a problem for low-wattage vapers unless they rebuild the heads themselves. The DNA 40, at $85, is the better choice and comes with a much higher capacity, albeit non-Li-Po battery. It is more than three times the cost of a 30W iStick, however. I still think there is a place for the iStick (30W), Defender, etc. For $85, we can get two iStick-like mods and a STMini, Lemo 2 or 3 GS Airs. For $85, an eVic-VT and a STMini might be the best choice and offer the most flexibility; even if one only uses the VT in VW mode.
So many options, too little time and money...