Every time I hear that Rails isn't scalable, I laugh. I work on an RoR site that handles millions of page views a day. The scalability solutions for RoR are the same as any framework: caching, database clustering, app server clustering, and load balancing. With a team of smart developers and sys admins, you can make any site based on a solid framework scalable. Since the poster's shop has extensive PHP experience, picking a solid PHP framework is probably best for him, although he shouldn't discount the productivity gains he may experience with Rails or another Ruby framework (Sinatra, etc.).