Finally, after months of waiting Oracle released Application Express 4.0 just a couple of minutes ago.
See also David Peakes Blog.
Don’t loose any time, go get it.
If you aren’t sure whether or how to install it, you also can use the SaaS-Instance on http://apex.oracle.com to give it a spin.
Have you already read the Overview about New Features ?
If you want to get an expert introduction into APEX 4.0 and you live near Vienna/Austria you should definitely book this workshop.
Enjoy Oracle APEX 4.0 and show all the Java and .NET guys how fast you can develop amazing applications!