I work for a reseller of Microsoft (and other vendors') software and have attended many MS presentations about Office vs. OOo vs. Google Apps. Microsoft is marginally worried about Openoffice in some geographies (mainly France where the government freely gives out OOo disks at the taxpayers' expense) but has a clear objection handling routine for everywhere else. Basically, Microsoft urges companies to to try Openoffice so that they can learn how dated and incompatible it is with the business world in general. They also push organizations to try Evolution instead of Outlook for the same reasons.
You'd be surprised how many emails we get out of the blue stating "we're an all Linux shop but we want an Exchange server with Outlook licenses for compatibility reasons. How much for a server and 100 seats of Office?"
Anyway, Microsoft's real fear right now is Google Apps. Everybody, even Google, knows how inferior Apps is to Office, but the sexy Google name greases the runway to bring this cloud-based office solution into more and more workplaces. Microsoft is fighting tooth and nail to prevent every single switch from Office to Apps. Openoffice is hardly on Microsoft's radar compared to Google.