I like to build and run my Xcode projects using the "Build & Run" command from the Xcode bundle, both for convenience and because my debug output and exceptions are formatted in such a way that it can be clicked in the output window so TextMate jumps to that section in the code.
With Xcode 3 that has become a little trying though: Every time the underlying xcodebuild command is launched, it goes through a rather lengthy "Checking Dependencies" phase.
Xcode itself seems to cache the results from that phase, it is only slow the first time a project is built after opening it in Xcode.
Hoping that it might help others, I came up with with the command attached below. It uses Xcode to build the project, and (upon success) hides Xcode and launches the freshly built application in such a way that the output goes to the normal "Build With Xcode" window.
If compilation fails, it leaves Xcode in the front. I set Xcode to use the "Condensed" layout, positioned the "Build Results" window to be the same size and location as TextMate's "Build With Xcode" window, and set TextMate as external editor for all source files. So double- clicking on an error message will still jump to that location in the code in TextMate, just like the original Build With Xcode" window would do with a single click.
Hope that helps someone, feedback welcome.
Gerd