Now that Mac OS 10.7 Lion is out, before you upgrade, use the Lion App Compatibility Table to determine if the apps you rely on every day will still work after you upgrade.
RoaringApps' table of Mac applications is arranged in alphabetical order, complete with the developer's name and website, the current version of the app, and its compatibility with Lion. Use the keyword search to find a specific application. Apps that are fully compatible have green checkmarks, and apps that are available in the Mac App Store have the App Store icon in blue next to them.
A number of apps haven't been tested, so your mileage may vary with your favourite apps. If you have an app that isn't in the database, you can submit it, but odds are most common applications are already included. Are your often-used apps ready for Lion? Share your experiences in the comments.
App Compatibility Table [RoaringApps]