I have only limited experience with Reporting services. I'll try to answer your questions, but others may have more complete responses:
SQL RS looked very impressive and included a lot of good stuff out of the box. The biggest drawbacks that I found were:
1. Requires Visual Studio .NET (or one of its components like ASP.NET or VB.NET). This is required to design the reports, so it appeared to be difficult to get a "lay person" to design new reports.
2. While I understood the snapshot capability (especially scheduled snapshots); it was difficult for me to understand how to distribute the snapshot reports over the internet (it seemed you were limited to either e-mailing them or saving them to a public folder).
As for licensing, the model is similar to Analysis Services. If you are going to deploy an "all-in-one" server (SQL and IIS), then you do not need a separate license. However, if you want to split the IIS components of RS to a dedicated web server, then you need an additional SQL license.