IBM Websphere Studio Application Developer 5.x and the newer Rational Application Developer 6.0 has good support for Struts. There are also some plugins for Eclipse that make it easier to develop Struts applications. MyEclipse also has good Struts support.
IDEA intelliJ is quite good too. I have been using it for about 2 years now. It has hot deploy where you can deploy your application without shutting down your container. I can also debug and does NOT require lot of effort setting it up.