Carrierwave vs paperclip vs attachment_fu ??

I need to upload not only images but also other files(excel, pdf's),

I would like to setup custom validations for the specific file
uploaded(size, format) and I am using rails 3

Any recommendations would be greatly appreciated.

Thanks

Go on with carrier wave. According to Rails cast it works perfectly on
Rails 3. See: http://railscasts.com/episodes/253-carrierwave-file-uploads