Importance field in shared worksheet

I'd rather use 'i?' instead of '!?'

Definition:

Important? (not equal urgent which is rather determined from 'Since' and 'Due' dates)
Value = A, B, C; +/- suffix can be optional.

This is derived from 7Habits concept. However, it looks not practical in sharing. Generally, people are familiar with priority to which urgency still dominates.