I got Applicant Lab after I wrote the GMAT and started prepping for application season.
I would actually recommend that you get a subscription while you prepare for your GMAT, this way you can brainstorm your stories slowly in parallel, say a story a week and by the time you have your score you will have 12-16 stories to choose from.
This is a solid tool in the sense that you do the hard work upfront in terms of why MBA, why a particular school, why now? and these things are important for you to understand before you commit to applying.
