I've been using Microsoft SSRS for 2 years. For me, the most valuable feature is the integration feature with our ERP. SSRS has room for improvement including drill down and graphs. Although I am happy with the products, I have experience performance degradation at times.
We're currently running both SSRS and Cognos. We ended up choosing SSRS after evaluating it alongside Business Objects. Once we chose to go with SSRS, we implemented through the vendor and found their level of expertise to be high which made the process very easy. I would say that our ROI is 200%. I would recommend SSRS to others.