Here’s the process I used to be able to compile Flash Player 10 files. I know this has been covered by others, but here’s what ended up working for me. Keep in mind I’m on a mac and use Textmate.

Step 1 Install Flash Player 10. Remember, as of right now, there’s no debugger version, so unfortunately you’re out of luck if you’re relying on Terminal to catch your traces from your browser. However, this blog links to what sounds to be a debugger version, but I was unable to install it. The installer repeatedly assured me there was nothing to install, whether I had player 9, player 10 beta, or no player all.
Update! I just came across this link which has excellent instructions on how to install the Flash 10 Debug Player. I never thought I’d be so happy to see some trace statements.

Step 2 Grab Gumbo, aka Flex sdk 4. Chuckle at the name. Copy the downloaded file to Developer/SDKs. You may have to authorize the operation.

Step 2.5a Peruse the Flash Player 10 documentation.

Step 3 Follow along with this video which covers how to publish your files from Terminal. Sexy! I only had to make one change to the Flex SDK to include our repository class path. Check the flex_sdk_4/frameworks/flex-config.xml and modify source-path to appear as follows:

/Domain/summitprojects.com/Users/lucas/Library/Application Support/Adobe/Flash CS3/en/Configuration/Classes/lib/

Now we’re mimicking the Flash IDE’s Preferences for global classpaths.

Step 4 Visit this page and build a Textmate command that will run your mxmlc from textmate without having to use Terminal. Now you’re efficient!

Step 5 Celebrate and use native 3D transformations in Flash!