I currently use variable voltage and I would find it hard to be without it now. Certain flavors are enhanced with different voltages. For example, I have a number of fruit flavors that taste best at 3.4v - 3.7v, any higher voltage and they tend to taste burnt. I have many coffee flavors that taste best at voltages between 4.1v and 4.6v. Just 0.2v difference in voltage can make a difference.
Imagine has stated that Smokeless Image's focus is on the beginner and intermediate vapor. The company uses the K.I.S.S. principle to good use. By keeping all of the gear compatible with one another it keeps everything less complicated, and that in itself is a selling point.
She has also conceded that customers may feel the need to move on to different horizons as far as different gear, which includes variable voltage, devices that utilize replaceable batteries, devices that are capable of carrying larger capacities of juice, etc., and the company is alright with that. It is a rather natural progression in the vaping experience. Their primary goal is to provide smokers with an new alternative to quit smoking, and I'm quite certain that they have done just that quite successfully.
Although my current supplies of Smokeless Image products is rather limited by the setup that I currently use, I am still loyal to the company and frequently recommend them as an excellent company to begin vaping with. They are, after all, responsible for providing me with my first starter kit that allowed me to quit cigarettes for the first time in 30 years of smoking.
Trying out an eGo Twist would not be a breach in loyalty to your beloved company. As someone has pointed out already, adaptors are available to allow intermixing of opposing devices. One could continue to use Volt devices on a variable voltage battery. In fact, I still use Volt ce3s on my 510 threaded mods to test new juice sample flavors. Used with a 510-to-808 adaptor, these are ideal for this use because I don't drip, they use a small amount of juice, and are reusable, unlike cartomizers.