Correct me if I am wrong
VB wont cause any more (and if so probably negligible increases) sweating than if you were in a room now. A lot of sweat may not be noticeable until you are in a closed system of moisture, but it may just be an extended feeling of clamminess that you experiance. As regards to your feet, feet are the sweatiest body parts (also you shouldn't sleep in VB socks because of over saturating your skin and causing trench foot, and it may be uncomfortable). This question is really something only you would know from personal experiance. Try spending a night at home or outside your home in a simulated test, and if you like it the sky is the limit.
Many people use VB clothes, which provide a closer environment, which MAY cause less sweating, and has the added use of being highly effective cold (10 deg F onwards) hiking apparel and allows you to use insulated clothing like down jackets into your system more effectively.
A good resource for vapor barrier information is RBH designs, a company in CT that specializes in it. Their reviews are probably the best experiance testimonials you can find. Stephenson's Warmlite also has an article on it, but it is highly suspect from what I've read and heard about it.
Also if you go onto itunes you could listen to Andrew Skurka's "Icebox Hike" trip reports which describe briefly (its a few minutes in quite a long podcast) his experiance with VB in both his sleeping system and for hiking.
PS welcome to the site!