You probably haven't noticed it personally, but did you know that banner notifications are supressed while the Siri interface is open? Well, to be honest, I didn't either, until I saw this tweak pop-up in Cydia.
The premise behind Unveil is simple, allow banner notifications to be displayed within the Siri interface. If you're someone who absolutely must have access to banner notifications at all times, then Unveil is something you should consider using.