The noise is one of the biggest problems of HDR. It can happen sometimes that we do not feel satisfied with the work achieved over just because the image is too noisy. Don’t worry about that: the noise is easy to eliminate, as there are several Photoshop plug-ins to do this. Personally I use TopazDenoise. 

TopazDenoise Photoshop plug-in offers the fastest and effective way to reduce heavy reduction noise putting unrivaled quality at your fingertips.