I am a big believer in the Tiles framework. It's main advantage, in my
viewpoint, is its ability to increase reuse across the presentation
tier of an application.
With Tiles a developer can set up a few Tile definitions (templates)
that represent the different page layouts across a web app. Each Tile
definition can have both concrete JSPs as well as empty Tiles. Then,
through Tile inheritence, each template can be extended n times to
create any number of pages. Say that a web app has a common header and
footer across 10 pages. Tiles allows the developer to create one JSP
for the header, one JSP for the footer, one Tile definition, and 10
JSPs for the body of each page. If the header JSP changes the change
ripples through all pages without any need to change the Tiles XML.
Sure, you could use jsp:include and get a similar result but you would
lose the flexibility of the XML configuration and the inheritence that
Tiles provides you. In the near term it will save development time
with each new page that you create that fits into one of the templates
you have defined. In the long run it will make the application much
easier to maintain.