As a rule, there should be only one handler for any given format. We are not sure about the product you mention. From our understanding it's an XP-era "thumbnail provider" using old interfaces (hooks) into Explorer that happens to work on Vista and Windows 7 thanks to Microsoft maintaining backwards compatibility (they probably needed it for some of their own file formats).
The product you mention does not provide WIC-enabled codecs for the image formats it supports, as we do, and as such probably does not provide the full user experience envisioned by Microsoft when they replaced the old mechanisms with the new WIC-based codec system introduced in Vista, namely integration with Explorer Preview and Metadata panes, viewing and slideshows in Photo Gallery, Windows Photo Viewer 7 and Media Center 7, as well as the all-important integration with Windows Search, letting users find images instantly by keywords (EXIF tags) or other EXIF metadata such as date taken or camera model from any Explorer search box.
Our WIC-enabled codecs provide all of this functionality thus go far beyond simple thumbnails!
There should be no problems running both product together although we did not test it so we cannot officially support it. It would be wise to configure each products during installation so there is no overlap between the formats handled, for example only enable the formats we don't support (yet