We have a young Newfoundland mix, who already has exhibited some hip soreness.  We got this ramp to provide a smooth entrance into and out of our SUV.  It is easy to install and stows in the back.  It is heavy and sturdy enough to be secure, while still being light enough to maneuver into position.  Our dog learned how to use it with 10-15 minutes of training: beginning with on the ground walkovers, then placing ramp over a few steps for a walk up, and finally up into the SUV.  Treats definitely help. 

Pros: Easy assembly, durable construction, ridges provide good grip for paws
Cons: Takes up a fair amount of room to store in back of SUV