Today Apple released Lion (10.7), the next major upgrade to Mac OS X. At the same time FileMaker Inc. released a new Knowledge Base article with details on Lion compatibility for FileMaker Pro 11 and FileMaker Server 11.
FileMaker Pro 11 is compatible except for minor issues with number and data formatting, and no support for the .xls Excel format (.xlsx is still supported). This is because Lion does not include Rosetta (PowerPC code) necessary to work with .xls files. There is a list of known issues (FMP) and a new update will be available in August.
FileMaker Server 11 is compatible except for Web Publishing and no support for the .xls Excel format. There is a list of known issues (FMS) and a new update will be available in October.
As I cautioned in my original post, MightyData strongly recommends a wait-and-see approach for any customers who use FileMaker 11. At a minimum, wait until the compatibility updates are available in August and October respectively. Contact us if you have any questions about Mac OS X Lion and FileMaker.
Update: There is also a Knowledge Base article describing compatibility for FileMaker 9 and 10. The short version is only FileMaker Pro 10 is compatible, with some known issues. Everything else will require an upgrade.
Update: SuperContainer, a document management framework for FileMaker, requires a free update to version 2.81, available now.
Update: CNS Plugins has announced their FileMaker plugins are compatible with Mac OS Lion.

Excellent summary!
Honza, thanks very much! I’m looking forward to seeing you at DevCon.