A while ago I posted a long report about notification problem - the biggest problem for me was that when I have IM+ on screen, and let the phone go into standby mode I am not notified of new messages because the focus is still on IM+.
This bothered me for quite a long time because I could not be aware of new incoming messages when I do something else and the phone goes standby because of inactivity.
I upgraded to IM+ 8.0.1 today but the issue is not fixed yet, so found somewhat temporary solution; use autolock. Set the autolock so that when your phone goes into standby let it automatically lock itself. The lock screen will steal focus from IM+, so it will produce notification for newly received messages.
The drawback of this workaround is that when you're running some applications that prevents the device from sleeping it will not work. A good example would be a music player application, like WMP or HTC music manager, which always sets the device active (even if you force set standby by pressing power button it will not sleep, rather it will just turn off the screen only). No standby, no autolock, so IM+ will still have focus and will not produce notification.
While I find this temporary workaround somewhat useful, I still think this notification issue should be improved from IM+ side.