I've got 'em, and overall I'm happy with them. That said, there are a few things that kind of stick in my craw.
I've got a new mainsail, which has yet to soften up enough to flake easily into the bag. Therefore, I've got to stuff, poke, and wrestle with it to get it in far enough so the zipper of the bag can be closed.
Secondly (and this is more a rigging issue than a Jack design problem) my reefing lines ALWAYS fall outside of the bag, and so I've got to manually stuff these into the bag before it can be closed.
But, all things considered, I'm happy enough that I aint gonna be taking the Jacks off to replace them with something else.