Then the simple solution is, of course, not to use it.
If you're not interested in doing an upsell at the POP, then you certainly don't have to. That doesn't mean that nobody else will want to use it, nor does it mean that your experiences are universal. On the other hand, upselling and impulse marketing does drive sales across the board -- be it e-commerce, retail, B2B, or anything in between. Frustrating or not, GoDaddy sells.
Hence my suggestion of having the option to present it either before or after checkout, with or without the ability to postpone payment processing until an upsell is selected or until a timeout is reached. Creating a table of rules based on order / account conditions with a "Present via: Checkout / Post-Checkout / Email" option would work wonders for the UI and ease of implementation, and would be supremely powerful.