[xsurf]

in this store (there is another completely diferent one not too far in the future), nutritional supplements.
Hmm... what I thought to do was for all the upsells for the products in the cart to appear (with those already in the cart to be ommitted) - so if someone buys products A and B, with X and Y being upsells for A, and A and Z upsells for B, then if both A and B are in the cart, the customer will be offerred X, Y and Z.

What you say does make me think. Most customers who come to my store though are interested in one specific solution, so the typical case will be that they will add the item, and either take the upsells offered or not, and run. My thinking is they will probably not add an upsell and then yet another, and so what is offered in the cart will be any way pinpointed, since they will just have one item usually. But I may be wrong.