Xcode 4

Have a look at the XCode 4 User Guide and the XCode 4 Transition Guide to see if it's worth getting.

The XCode 4 Transition Guide also talks about opening XCode 3 projects in XCode 4.

 

Xcode 4 is worth getting.

The workflow under Xcode 4 is smoother than under Xcode 3 for me. I'm speaking mostly about running to IB and back - that's all gone now (IB is just another editor in Xcode 4, like the text editor used to edit code).

Also the keyboard shortcuts and the various editor and utility windows seem to make more sense to me. I use Xcode 4 in full screen and turn off/on the editors and utilities as needed and it feels very productive.

In terms of moving to Xcode 4, you probably don't want to do it in the middle of a critical project. However, if you have a non-critical project you're playing with, fire up the Xcode 4 documentation (see the two items in the earlier reply and http://pragmaticstudio.com/screencast-tags/xcode4), then dive in with your projects. Learn by doing.