So far I've gathered the below from trial and error along with other community posts: 

Cannot preset package details and weight.
Cannot use customers shipping account.
Multiple packages in one shipment is not possible.
Negotiated shipping rates are not properly implemented.
Previous manager allowed your invoice number to reflected on the label.
There are no reports that can be downloaded.
If you have different locations with different UPS account numbers, the system does not allow this.

I'm sure a community manager will reply with some boilerplate response that provides no solutions or answers.