We evaluated Demandware last year. Here are some of my team's impressions:
- Excellent support for mobile devices, which is important for us
- Social hooks into FB, etc.
- I like the dashboard which provides centralized access to all management, policies, rules, etc.
- Extensive partner ecosystem
Room for Improvement:
- Our architecture team raised questions about how it would fit in our environment, as there would be a good amount of internal work to get everything integrated together. You may want to look into this as part of your evaluation. It's not SaaS after all.