I've been away from ENworld for about a year, and it's like a breath of fresh air after going on the WotC boards. Thank you, everyone here.
On the subject: I have decided I will like Tool Proficiencies IF they have done something about the Climber's Kit, Disguise Kit, and Healer's Kit to make it so they provide SOME kind of benefit to characters who are also Atheletes, Charlatans, and Medics.
Players just keep taking BOTH because it's logical, and get frustrated to find they don't DO anything together.
Allowing Stacking would do it, but inflate the numbers, though it makes sense that Tasks that require (or greatly benefit from) tools would be Hard DCs wtihout them, so making them Hard DCs in the first place and allowing the tools to stack would probably do the job.
It would be more interesting, though, if the tools did something else, like increase the climb rate, allow you to not make deception contests with NPCs unless you directly interact wtih them, and provide better healing respectively. (I suppose the last already works that way, it's more a matter of the Medic skill barely doing anything without the kit than the other way around)