I've had a Tesla for about 9 months, and a Vamo for about 6 months. They seem to have the same chipset, although I'm not 100% certain of that, because they operate in the same way. Personally I prefer the Vamo over the Tesla and have relegated the Tesla to backup duty. This is mainly due to the larger diameter of the tube, it just doesn't fit in my pocket nearly as well as the Vamo.
As far as reliability goes, I haven't had a problem with either of them and so far would recommend them to anyone who's interested in a lower cost vv/vw mod. The main drawback to the Vamo is the very poor finish. Within a couple of weeks I had worn through it near the fire button, and the wear keeps showing more each week. That doesn't affect function however so it's no biggie in my book.