We have a report from a user that Hook can consume large amounts of CPU and large amounts of memory. This is not something we have seen ourselves or other users had told us about, so we cannot estimate the % of users that might have it. However, the report is definitely of an issue. If you experience this issue, please respond to this thread.
I upgraded to the latest version this morning and am using Hook for a research project on the Mac. So far no indication of memory issues. Hook itself seems stable, at least insofar as it stays running over log periods.