Yes. The "Plus" item you paid for and installed is just the license. You need to download and install the actual free app which I believe is called the JuiceDefender Beta. If you already have the "Plus" license, then it will enable the Beta version to the paid "Plus" level when you start it.
Here are my latest observations. I tried using the default settings and got some improvement. I then decided to try customizing the settings for each app. I proved that I'm incompetent at making correct decisions, and the results were erratic and poor performance. I managed the settings to the point that the phone simply didn't work. It said it was working, but nothing happened when I tried making calls. And, it didn't receive them either. I went back to the default settings (shut off the customization) and it went back to normal. But a word of caution: I still had occaisional problems with the phone going into sort of a sleep mode where it wouldn't receive call or let me make them. (Rebooting the phone takes care of it.) I'm currently running with JuiceDefender disabled to see if this problem persists and I may have to uninstall it if that's the case. By the way, if you uninstall JuiceDefender, just uninstall the Beta app and not the "Plus" license. You can keep that without issue.