Yes it will be useful because of so many reasons.
First of all, your already qualify for Express Entry pool as far as you qualify for FSWP 2014, because to enter into pool you need 67-points according same method as was for FSWP2014.
Secondly it will not have any negative impact on your already submitted application for FSWP2014, but it might increase your chances of getting selected under Express Entry prior to decision for FSWP 2014 comes.
Therefore apply for Express Entry without any fear and without paying anything extra. Because to make profile for express entry it is free.
Regards,George,
Doha,Qatar