ROR and MSSQL server

Hello all.

I have just gotten the Agile development with ROR book and am
evaluating whether ROR would be suitable for our needs. After reading
some of the book I am thinking that ROR might not be able to handle
the GUID datatype as primary keys in SQL server. Specifically primary
keys in SQL server are created after the record is created and might
not be available to the activerecord unless the record is reloaded
which would be a performance hit.

What is the proper way to handle GUIDs with ROR . Can I create GUIDs
in ruby and then pass them on to the server? This might be a good
solution.

Also what is the state of the freetds adapter? Is ROR+SQLserver ready
for production?

Finally. Presuming that ROR+SQL server is not ready for production do
either postgres or mysql have GUID data types?