While it isn't something we do everyday, I have had occasion to ship - or have shipped an item for a production. Where it be a large prop or rental scenic unit, or specialized equipment, there has always been a bit of a debate about how best to ship the item (Fed ex, as commercial freight and so forth). Add to those options a new one: Uship. basically the idea is that you put in a request and shippers bid on transporting your item. You can check feedback and choose based on their reputation and price. They can cut you a deal since they are primarily putting your package on a truck that has otherwise empty space.
The disadvantages that I see would be time: you may not be able to turn over the load quickly or get through the process quickly. The second would be dependant on how the organization deals with purchasing. i know some theatre I worked with that an unknown carrier would need to have some processes in accounting prior to being able to use them, which in a process like this could be a drawback.
The advantages would be cost, and potential time savings. If you deal through this company and didn't spend as much time dealing with calling around you could save time. You could however use their site to locate services, as they have thousands of transportation services listed.
So the next time there is something large to ship check out http://www.uship.com/.