yes - there is a special feature where if it discovers a competitive product it works out your banking details and sends all your money to Nigerian scammers
No, seriously - you can mix pretty much any file encryption, DLP, and disk encryption products together on the same system, they all interface at different levels.
You will of course find that using more than one solution from one vendor has added advantages though - for example, EEFF and EEPC from McAfee have AES-NI support in the latest versions, so encryption is significantly faster (20%+). McAfee DLP and EEFF work together to do content-aware encryption, EEPC and EEFF work together to do seemless login etc.
But, you can mix and match if you like - you'll just have to manage the products in separate places.
Thanks for the information, very helpful.