Probably doesn't help much that VRML kinda died on it's arse and never got out the novelty factor.
People just want to shop quickly without much hassle.
You want to really give them a better experience then combine both ideas.
Have them access the store online like you would normally, but the products themselves could be 3D Windows that allow interactivity with what your buying to find out more information.
Much like how NVIDIA have thier X-Box Website structured. You can play about and see the processor capabilities by holding the mouse over it and such.
There are many online 3D Content creators which make this possible with little down-time for the shopper. If you provide for them a 2D Image as an alternative while the Shockwave3D/Viewport/VRML is loading then that won't annoy your 56K users not seeing what the product is like before hand.
Providing some nice animated actions throughout the store would also help, like small flash button animations.
But as I said before, try to keep things simple. Remember not everyone has the most top-end systems or connections.