Having both the regular price of a product and the sale price (or customer specific discounted price) saved with the cart and purchase order. This can be handy for some reports on purchase orders or just to compare the savings per purchase order...

If you have a requirement to make one of the system fields read-only or “Not Required” for customer contact object in the admin->commerce manager –>contact->Edit screen here is how you can achieve it. It is rare requirement but does come along.....