There has been code written for the UPS module to print labels, but it hasn't been in the repository for a while. I had been confused by the various XML Tools that UPS provides, and I had made a quoter that used the Shipping Tool, but that is a premium service and most people couldn't use it. Since your original post, I've been working on reintegrating the order fulfillment with the newer quoting module.

As long as your account with UPS is set up to use the "Shipping XML Online Tool" and I've committed the changes to the module, you'll be able to create labels based on the information in your orders. Documentation hasn't been written for it yet, but that will be done soon as well.