1) Pitch Tracking - use it to do a key follow type of filter modulation or pitching your oscs or other sonic mayhem.
2) Gate/Trigger - Set a threshold level to trigger envelopes or the arp
3) Some kind of gain and metering - I know the BPM/LFO LED follows along with the external input level, but its hard to know when you're getting a solid input level.
That's my 3 cents.