The lavatube is not as great as everyone would have you believe. There are other APVs on the horizon in the near future that are just as good as it is for much less money. Besides the Lavatube 2.0 is better and it's about to come out any day now. Reviewers on youtube already have advance models to try out for their reviews. The Vario and the Apollo VTube come to mind as two APVs are as good if not better than the original Lavatube 1.0, and maybe even look better too.
The problem with the Lavatube is that you pretty much can't use dual coil (or triple coil) cartomizers at their full potential. For some reason it has a safety circuit that prevents it from vaping them above (IIRC) 3.8v (at least somewhere very near to that). It literally lowers the voltage without telling you (and here you are jacking it up to 6v thinking it's making a difference, like a dip). On top of that it almost never actually gives you the voltage you set. It's a very inaccurate device. Is the Lavatube great? Not for the money in my opinion. Not with the Twist out now and the new Vario on the horizon.
Another factor to consider is the amperage of these devices. What's amperage all about, you say? Well the higher the amperage of the device, the lower the resistance required to vape at higher voltages. For example, a lower amperage device at 6v might require a 4.5ohm atomizer, while the Provari does great at 6v with a 3.0ohm atomizer.
For the record the Provari has 3.5 amps. The original Lavatube has 2.5amps (some argue it's actually at 2.0amps), the rumor is the new Lavatube 2 has 4.0amps, and the Vario has 5 amps. The Twist, to be clear, all you need is a 1.5ohm-1.8ohm for low voltages, 2.4ohm for mid range, and 3.0 for maxed out voltage at 4.8v. Amperage really isn't a factor for it since you're not going into that hard-to-find and limited option area of above 3.0ohms (unless you are rewicking your own high resistance atomizers for the Vivi Nova or Stardust for example).
The Vario can be found here, but you can't buy them yet:
http://www.vaporbeast.com/SearchResults.asp?Search=vario&Submit=Search
That's right, $79 for just the APV. No word on what the kit price will be but it will include a charger and a carry case. It's unclear from the site whether it comes with a battery or not for the $79. Also, the Vario has a new connection design that will allow you to use cone threaded devices like the Stardust and it's supposed to improve airflow. The Provari, Vtube, and Lavatube all require a separate adapter to use a stardust because they lack ego cone threads that stardusts attach to. Vaporbeast, if you ask around, has about as good of a reputation on the ECF as you can get.
All that said, don't discount the Ego C Twist. Most people pick a sweet spot that's just above 4v anyway (unless they are a reckless throat hit chaser) and it goes to 4.8v. Also, carrying a long, skinny Ego C Twist in your pocket is arguably easier than carrying around a trumped up flashlight in your pocket. Also, at a tiny fraction of the price, it's a must have in my book. Even if it's only your backup. My ultimate setup now will be the Vario and an Ego C Twist or 2 with some vivi nova minis on the Twist and regular size on the Vario.
edit: They dropped the price of the original lavatube 1.0 to blow out their stock before the Lavatube 2.0 comes out to $54.99. I still can't say it's a great deal, but if you want one - you want one. Keep in mind you'll still need 2 batteries and a charger and it's likely going to bring it up over $100 since you'll have to order your batteries elsewhere and pay for shipping.