Does it keep the table of contents?

Well, this app has been great to me but it seems like this functionality is in Preview with Leopard now so I may not need it anymore. Drag the mini-icon from one preview instance's title bar to the sidebar of another open preview window and bam, they're merged. Other neat features like this have appeared too.. check macosxhints.com

This is an excellent app - functional and simple to use. This is how everything should work.

Allows you to rearrange the order of the pages, to add jpg to the stack. Stable, with no unnecessary options. I would recommend it over other solutions, even commercial ones.

As magnusvk pointed out the name does not include an apostrophe.

This app is really called "Combine PDFs" not "Combine PDF's" as should be quite obvious from English grammar.