Metavis for SharePoint
We used Metavis to migrate from SharePoint 2007 to 2010, it's a great tool to use and much better value that the majority of its competitors. I would recommend it. Great support and helpful staff really make the process a lot easier. A great feature of this tool is you can really think about the taxonomy of your documents applying new Metadata in the copy process, this for us was its biggest selling point.
Easy to use - we were able to simply install and go without any awkward configurations.
Great comparison features that enables you to see exactly what's in each site you're looking at.