It was an invaluable plugin once I figured out how to use it, but I'm definitely rating it lower because of a huge bug. See this thread: http://wordpress.org/support/topic/import-feature-does-not-import-file-attachments?replies=23
Basically, it doesn't download images if you select a subset of posts. Works if you select all but if you try to filter by date, category, or author it doesn't work. Awful. And the fact that the thread was closed without a response is just pitiful.
But, once I accepted I just had to download everything it got the job done. There are some other issues too with how authors are imported which is why I can only give it 3 stars. If it was just the image issue I would have given it 4.
Regardless, you really can't migrate a site without this plugin and once you figure out your process around its bugs, it is basically invaluable.