I have the Singles Playbook and a couple of other courses I purchased. Singles Playbook is one of Will's weakest products, I don't recommend it at all.
Also, these days he seems focused on pumping out more and more products (some pretty substandard) and doesn't check back on his previous ones. There are portions with missing videos and he doesn't reply to comments or address issues.
My latest purchase is Ian's (essentialtennis.com) Singles Domination. His videos are not as high tech and nifty as Will's but he's a lot more down to earth and sincere and replies to every comment and question posted.