Data warehousing often involves star schemas, which means lots of joins in your queries. I'd love to see how a real world OLAP tool performs on this.
The main issue with Redshift is the lack of multiple sort orders on a table. Take a look at our blog post on first impressions gleaned during the preview. Disclosure: we are one of a couple of systems integrator partners for Redshift.
http://www.full360.com/2013/02/14/aws-redshift-full360-first...