What would be nice is if they could integrate somehow. I saw in the comments for popup 7 that people complain that it doesn't mesh well with the statusbar. What I'm thinking, if it's possible (and I don't know seeing as I'm not a developer), is that the statusbar could glow the same color as the popup notification. The notification part could identify the type of message (e.g. 1 new text message) on the left side and the 3 wp7 menu dots on the right. Tap the 3 dots and it extends down to show the popup 7 information. Basically the only real integration I see needing to happen between the two apps is if there is a popup notification and it is set to teal, the statusbar becomes teal as well so that there isn't a black bar, then a teal bar, then the rest of the screen, for example.
This is funny that so many people are mentioning this just after a discussion with the developer of Popup 7. We are working with one another to get the two applications to work perfectly together. The first and most important step is to automatically move the popup notifications below StatusBar+. From there making the status bar transparent during a notification and having the accent color as the background is the next step. The idea is rather than duplicate functionality have the two applications operate optimally with one another. It is also great for people who may only want one or the other application's features.