Geertjan Wielenga has blogged about running the Wicket Kick Start Project in NetBeans. Check the Kick Start project out if you wish to jump start your Wicket development, and use the description of Geertjan to do so in NetBeans. Other IDE's currently supported are: Eclipse and IntelliJ IDEA (for IDEA: temporary download here).
It is not by intention that we don't currently support NetBeans, we just aren't NetBeans users. It is a matter of preference, taste and like it/hate it (this also goes for Eclipse, which also has many followers and haters). Perhaps someone will switch to NetBeans when the 4.1 release comes out?