Well x64 version will be required in the future, as only x64 codecs may work with x64 mpchc and x64 decoders. Though here I haven't found any particular video yet which would consume substantially different amount of CPU% on x64 compared to x86. Maybe when lots of additional post-processing is involved, decoding itself doesn't load CPU differently.
Though recalling how much time required to persuade Haali to do x64 version
)) He resisted for more than a year before finally surrendering :P