Ventile's chief attributes are its soft hand, windproof quality, and high breathability. It works great in cool-to-cold, dry conditions. It's also fine when it's cold and snowy out. But it works less well when it's raining, for instance. The stuff has good water repellency, but in time it will start to absorb water. When that happens, a jacket made of Ventile quickly becomes a heavy, soggy mess that can take days to dry. I used to joke that my Ventile jacket had the water repellency of a sponge: Meaning, it could absorb only so much.
Anyway, in the U.S., Gore-Tex pretty much killed off Ventile, even though Gore-Tex is more expensive, less durable, and less breathable. But, people went for its superior waterproofing (myself included). Ventile has remained moderately popular in the UK, and some makers can be found there via the Internet (try www.west-winds.co.uk to see some lovely but wildly expensive Ventile pieces). At present, I'm not aware of any U.S. gear makers who still make products using Ventile.
Is Ventile worth the money? That's hard to say. But you're probably looking at $300 and upmaybe way upand for that kind of scratch you can find some pretty nice jackets made from other materials. But the stuff is comfortable and versatile, so there's that to consider.
As to your other question, Nextec is a company that makes Epic, a fabric process in which fibers are encapsulated in silicon. The result is supposed to be a material that is highly breathable and highly water-repellent. The Epic process also can be applied to a wide range of materials, from nylon to cotton.
I used an early-generation Epic jacketa light windshelland was decidedly underwhelmed. I just didn't think it breathed that well. And in fact, the stuff isn't being widely used by shell makers these days; a few tried it and then discarded it. Epic has caught on with sleeping bag makers in some cases, and the U.S. military has used Epic in some of its new all-weather uniforms. I think the technology is highly promising, but at this time I'm not a big fan.