I personally find the discovery engine completely inefficient. Why is CDP or other, not used to aid discovery? I could simply then scan 2 /24 management networks to discover our L3 devices, then use CDP to discover all connected devices... Currently I have to scan a /18 network to discover all of our nodes, which takes hours! Not very good when I simply want to discover a single node I have added.
While it is of course possible to then create smaller discovery profiles, using CDP or other would decrease this discovery time immensely.