Yesterday I had all of the following versions of NetBeans installed:

3.6
4.0 beta
4.0 final
4.1
5.0 developer build
5.0 final

I have just uninstalled all of them except for the last. I guess it's a good thing that unlike most software from Microsoft, most open source programs (and almost anything written in Java) are happy to have more than one version installed on the same computer. On the other hand, it can contribute to cruftification if you're not careful.