A neat trick found here for an easy way of doing custom logging to SQL Server. Essentially you can hack around with the stored procedure that SSIS calls to log events (sp_dts_addlogentry).
An obvious usage would be to simplify the extremely verbose logging messages provided by SSIS by filtering the majority into a seperate table and 'cherry-picking' the really useful ones and INSERTing them into a 'core' logging table. I'll leave it up to the reader (if there are any!) to work out the 'usefulness' algorithm for now, although I may post on this again if I end up implementing it.