I've been vaping the Nautilus now for several months. All the above posts are good info. When you change a head you have to let it sit for a few minutes to saturate the blanket inside that delivers juice to the coil and wick. You can also drip a drop or two in the head from the top and let it sit for about 30 seconds and then blow it out into a towel and install it. You can vape immediately after that.
I vape my 1.8 ohm coils at 3.3v and still get warmth in the vape. These coils are highly efficient and don't require higher voltage. 3.3v will give you a warm 6 watt vape.
Now, there are issues with some of the coils in distribution and Aspire has sent bulletins to vendors outlining a problem they had with wicks that were too small. These wicks didn't contact the coil enough to produce good vapor.
I've also encountered a new problem that hasn't been broadcast. A few days ago I went over to my B&M store to swap out some bad heads that the dealer had agreed to do according to the bulletin from Aspire. She swapped 5 of my bad heads and I bought 3 new ones. Thenew ones last about 3 hours or so and then the vapor falls off. I'd crank the voltage up a half a volt and the vapor would improve, then die again.
I checked the resistance and found that my 1.8 ohm coil was reading 2.4 ohms, then 3.1, then 4.2 and finally up to 7.4 ohms. It rose as I vaped. I continued to vape one of those until it finally read open. I verified all of them by ohmmeter. I thought I was losing contact with my mod. That wasn't happening. It was internal to the coil. I've gone through 6 in a row that did the same thing on two different mods. I saved three of those for the vendor to test, assuming that the last three will fail like the first five This morning, I'm going back to the B&M store for a talk and hopefully some relief on the coils. These are over $3 each when purchased singly.