I use the "free" version. It shows me fare bucket availability on most carriers (the same f9 a9 y9 b9 etc format). But, some of the cheaper buckets that are still available through consolidators don't show on KVS. Maybe I need to switch the GDS that it searches to be able to see those too.

One thing I really miss not being able to do is see award bucket availability on LH/UA/SQ. For some (unknown) reason, KVS is unable to show those. From what i have read, even the paid versions don't offer that. So, i am guessing the *A carriers pulled that out of the GDS.

I use the KVS tool in combination with the *A electronic timetable to decide routing. Being 2p, i get E+ seating. but occasionally when my wife or kid come along, i end up having to buy a E/M/U fare for them to get one of them into E+. In such situations, its easier to use KVS than United.com's fare availability feature.