After researching various diverters I selected the Oatey Mystic Rainwater Collection System. It is easy to install in 4 steps and the only difficult (and LOUD) part is having to hacksaw out a 6 inch section of the downspout. Be sure to put cardboard or a similar item to protect your siding from the hacksaw. You can also use a rotary tool to make the cut. You will find that most, if not all, systems require you to cut into your downspout to insert the collection system. The Mystic system fits snug in your downspout so no screws are required to attach the collection unit to your downspout.
My only complaint is the hose needs to be warmed to take out the bends. Don't expect to take the hose out of the box and immediately use it. It has been a cool spring here so I put it in the oven for about 15 minutes on warm and then stuck a PVC pice into it to remove the kinks. The instructions say to put it in a warm place for a few hours.
Because this system works best with a closed rain barrel system I had to convert my open system rain barrel to a closed one. That was not all that difficult and we are back up and running.