The templates are free. It is only the Task Board Application that cost a modest fee. You can use the templates without the Task Board although I highly recommend using it as wll. I think the biggest advantage for my team has been that the ScrumForTeamSystem tempaltes integrate into VS and provide a seamless feel with the rest of the development environment.
We love the ability to attach the PBI's to check-ins and have them show up on the Daily Build report.
If you are are missing something you need, you can fire up the VS template editortweak the templates to your liking. For us, we added a "Requested By" field and a "Testing Status" field to the PBI template.
The 2 shortcommings that annoyed us were that the "State" of the PBI's were not the same as SBI's (No Ready For Test on the PBI). We do testing/validation at the feature level and not the task level and wanted to track the PBIs status so we had to add our own custom field. The second issue was that there is no report out-of-the-box for a PBI burndown/up at the Sprint level. So you can't see how you are doing at delivering stories, only tasks. You have to make your own.
We don't really use the "Bug" template much (we ship flawless code:) ). No really, there is no such thing as a bug against work in a sprint; so the only time we record a bug is if a client finds an issue in the production code where it didn't work as advertised.
As Vaccano said, it isn't nearly as fast as a whiteboard or post-its in a meeting environment but if you get a couple people really good at using the tool and a couple of laptops you can make it work.
I evaluated several products and the simplicity and price of ScrumForTeamSystem can't be beat.