For those of you looking for more resources on this subject, I have two articles related that cover some of the same ground:
Interacting with Office in SSIS
My #1 caution for those using Excel or other Office documents is to use the providers, and not the COM API, due to the Considerations for server-side Automation of Office.
For the ultimate discussion of problems, solutions, and workarounds for Excel issues in SSIS, you need to review Douglas Laudenschlager's series of posts.
Todd McDermid - SQL Server MVP, MCTS (SQL 08 BI), MCSD.Net
My Blog - Dimension Merge SCD Component for SSIS - SSIS Community Tasks and Components