I tried it for the same reasons. I'm often very forgetful and I find it hard to focus sometimes, but funnily enough some of my highest scores were in Memory and Attention.
Without full access, though, you may improve, but you'll never really know whether your BPI is satisfactory. I played around with it for 20 minutes and got a BPI of 809, but I'm not certain if that's good or not because I can't compare my scores.
And I think having various options of games is important because most people will find some games easier than others, even if they're in the same area of brain training.