As per issue #28, there appears to be an issue with the dependencies specified in MetaWhere's gemspec that block using the latest version with Rails 3.1.0 RC4.
updating arel dependency requirement
updating active record and active support requirements
another tweak to active record and active support to include RCs
I see the recommendation to use Squeel for edge rails. Seems like this is not needed as a result. Closing. Apologies for the noise.