I'm coming late to this game, but I had googled boomkicker because I just saw a 30% off advertisement, and got this thread. I assume sailingdog "a true topping lift gives you another halyard" is talking about tcase10 who says, or said in 2008, that he didn't have a topping lift. If I were to get a boomkicker I assume there's still room to keep my existing topping lift either connected to the boom as a spare, or both ends cleated to the mast.
That still leaves one with the problem, mentioned in a couple of posts, of having more stuff aloft than you need, in which case one has to decide if it's better to have and not need than need and not have. Just how much trouble does this relatively light 'halyard' cause if nicely secured to the mast? I imagine if it's loose it would slap against things in the wind. Would it really make enough difference to performance that I'd lose in a close race?
And I'm talking about adjustable topping lifts, essentially small halyards from the boom's aft. Some posts have talked about fixed topping lifts, both the kind that are short lines or wires clamped from the backstay and clipped to the boom's aft, which I also have, and folks have told me not to use it, because I often forget to disengage it when I've raised the sail.