For the pairs I've used the insert system on i've never had a problem with pull-outs, the bigger threads and epoxy mount is stronger but, with that extra strength in the mount, if you do manage to pull out the binding, your skis are toast. The size of the hole it would pull is well beyond any sort of repair that would compensate for the structural damage to the core.
As for how difficult it is and the cost for a shop to do it, the way I managed the costs while still getting an accurate mount was to have my local shop just drill using their jigs as if they were going to do a traditional mount but not put the bindings on*. I paid normal mount price for this as its the set up and accurate drilling which is the major part of the mount cost. I then did the binding freedom mount myself, overdrilling the shop's holes and tapping them. It's best to do a few dry run 2x4 insert mounts without epoxy to get used to the tapping as, depending on your ski construction and the core wood, its easy to over-thread the holes. It's time consuming but worth it to save on bindings.
* I understand this might not be an option for some with shops charging high costs for mounts already and having strict poilcies about skis they touch needing complete mounts. You could always just let them do the full mount and back their mount out carefully once its done. I was friendly with my local shop & tech and so they were cool with it as they knew I wouldn't come back to them if something eventually went wrong with the mount after I insert drilled them.