The really really really cool thing is the backwards compatibility for Office 2000+. If you've ever been frustrated by Office Automation, now you can kick Excel to the curb and say "no more"! :) Products like ExcelWriter with their $10,000 site-licensing fees will no longer be necessary.

Anyone will be able to spit out an Office document in an automated manner without expensive tools, without interop, and with enough backwards compatibility to not have to care. It'll sure make my job a lot easier.