I have a Vamo V3 that I bought around Sep/Oct 2013 and it still works, and I wouldn't have a problem with recommending the 20 watt version, especially at that price.
But.
A few months after I bought mine, the 510
threads were completely stripped out. Rather than steel, they chose to go with (I believe) plated brass for the 510 connection. I bought a replacement top cap on line, and after about 30 minutes, I got it soldered in and replaced. I don't know if they have improved on that design.
There are a lot of folks on this forum that have been using the Vamo for a while without issues.