VBL has its uses in various "modes". I always use VBL in my boots for winter, esp. for backcountry skiing and snowshoeing. My favorite is a thin diver's sock of closed cell neoprene over a thin polypro sock liner. The sock liner gets replaced with a clean one before bedtime. There is no other way to keep the insulated layers of your footwear dry from inside dampness. The cheapest warm footwear is feltpacs, but from Cabela's or Gander Mountain or Bass Pro Shops, NOT Walmart or K Mart. Military "Mickey Mouse " winter boots are very good and have their own built in VBL sealing the felt insulation. The military knows about VBL for footwear.
All this footwear info seems heavy and it can be conpared to light summer shoes or boots. But winter camping itself means moer weight for clothes, fuel and even food. Winter is no time to skimp on safety items such as food and clothing.
For sleeping bags, as mentioned, a VBL is worse than useless if you plan to wear extra clothes to bed. It will wet them out. Where a sleeping bag VBL liner IS good would be on a week long winter trip where you want to keep the bag (esp. down bags) from accumulating moisture. Accumulating moisture in the bag's insulation is unavoidable W/O a VBL, regardless of how often you air out the bag in the morning. Most of the accumulated moisture freezes when the bag is aired out. (Remember the frozen down bags of Scott's tragic South Pole expedition for a cautionary tale.)
A VBL bag liner can be made from light urethane coated ripstop from, say, Seattle Fabrics who has a nice aluminized WP ripstop. You then seam seal it at home. Be sure to make a drawstring W/ cordlock at the top shoulder area for the VBL to keep moisture from your bag. A warm balaclava is a must for winter camping, both for sleeping and general use.
VBL clothing, such as a VBL shirt, is good for keeping down garments dry if they must be worn while travelling. But remember, waterproof breathable garments are not VBL and can't be used as such.
*** I recommend you wear a layer of light polyester or polyurethane long johns whenever you use any VBL so it can be dried quickly. That layer will keep you from feeling the clamminess of the VBL layer against your wet skin.
BTW, don't forget to contact me. I left my info at OM.