This link has a pretty good list of advantages and disadvantages.
To the advantages, I'd add that Struts is a good way to keep large web projects well organized. If developers know Struts, it's pretty easy for them to find their way around any Struts project even though they may not have written it or be familiar with the model.
I'd also add that Struts is by far the most widely used Java Web Framework. By using Struts, you have a large body of developers who will be able to understand your application.
To the disadvantages, I'd add that it's getting to be a bit dated. The Struts that we all know is referred to as Struts 1, and it's pretty much at the end of its development cycle. Struts 2 is soon to be released, and it's quite a bit different in that it's built on the WebWorks framework. Also JSF seems to be gaining ground in terms of its acceptance as the de-facto standard of Java web development.