The plugin used to be free until February 2011.
THere are currently some concerns regarding this plugin:
- the access to the WPML support forum is limited to paying customers
- solving interoperability issues with other plugins is really hard, especially because the forum has restricted access and secondary because of the plugin is commercial (other plugin authors may not be so willing to spend time debugging compatibility issues with a commercial plugin).
- the forum closes the questions after two months, so you may encounter old problems that are not solved and you cannot reopen them.
- some people were really disappointed about the commercial approach, especially because the free/old plugin breaks when you upgrade wordpress
- some people complained about the fact that the plugin is focused mostly to use the iCanLocalize translation service instead of other translation approaches, like in house-translation or crowed-translation.