I've just released the 3.0 gem of Client Side Validations
It is a complete rewrite and supports all Rails 3 validations (falling back to server validations if it makes sense), nested form fields are now supported, Mongoid 2.0 is supported, custom FormBuilders like SimpleForm and Formtastic are supported, custom validations
are supported. Client Side Validations now has a system of callbacks
for more control over your error rendering. Check out the Blog post
to get started!