Is it worth getting the Porter cable polisher? I usually polish by hand but it this thing makes it easier/faster then with five vehicles to polish/wax I might ask for this for Father's Day. 
For doing that many vehicles, it should be a good investment. Especially for that price.
Yes it's worth it! Adam's also includes the backing plate which you know for sure works with their pads. Plus for dad's day use DAD16 for 15% off plus ship is free. $127.49 at your door.
Amazon you still need to purchase a backing plate and usually pay tax now in many states