IBL on its own IMO doesn't give good results. You need to turn shadows off on the IBL light, and add separate light(s) for shadows and specularity. You can use ambient occlusion with the IBL, or better still use AO nodes on relevant materials - Occlusion Master in the MP will do this very easily for you. Then you should get pretty good renders. This is just my take on it - fully expecting to be corrected by others!

Steve