http://www.eclipse.org/documentation/. For example "Eclipse Ganymede Documentation (HTML Help Center)" is for Eclipse 3.4.The same documentation is available from Eclipse menu Help > Help Contents.Start with Workbench User Guide chapters Getting Started and Tasks.Really useful and relaxing is the Tips and Tricks chapter.
If you have installed the platform, you can always take a tour from menu Help > Welcome.
There is no experience compared with practice, especially for GUI intensive apps.
You can browse for more resources in the Eclipse site www.eclipse.org with good articles and responsive communities available.
Be prepared to discover nice functionality all the time. From time to time we recommend to read tips, tricks or concepts.