The benefit of lifters is that you're higher up off the ski, thus better for carving.
Unfortunately, you apparently get less feel for the flex of the ski with the lifters. You don't flex it as well (similarly to having track/demo bindings) and that supposedly affects the way you ski. I have lifters under my P12s on 2 of my pairs of skis and I haven't noticed anything; not that I've tried both ways, but its really not a big deal.
The reason they can't mount them with the risers is because the binding is what holds you into the ski, and tampering with it could make them liable to a lawsuit if anything ever happened. Plus grinding down the screws/finding new ones is a pain in the ass.
Original Thread: "If you suddenly skied off a huge fuckin cliff and you only had time to throw one last trick before you died, what would it be?"
Malcolm: "id probably just flail my self to death"
Check these out and tell me what you think!: