The Amputator is not an unpopular weapon but it’s certainly not the average Medic’s first choice. I know of far more people who main the Ubersaw, and after that I’m pretty sure the Solemn Vow is second place. I totally get that; the Ubersaw’s reward for landing even a single melee hit is incalculable, and if you’re going to sacrifice that you might as well grab a passive upside like seeing enemy health. Passive upsides are extremely powerful.
But when you’re going to choose a non-passive upside, survivability is a nice one. And it’s amazing what +3 hp/sec can do to get you out of a tight spot if you’re moderately good at dodging and abusing corners. Which you should be good at if you’re playing medic. Remember that the Medic’s natural regeneration is stymied by being dealt damage, so you’re at your most vulnerable in the very first second of the confrontation. The Amputator is for the Medic who favors flight over fight, who’s so prepared to turn tail and flee that they’ll even switch to a -20% damage melee weapon just to hammer home how unprotected they are. That sums me up pretty well, especially when a large part of my gamesense is making sure I’m not overextending.
I think it’s an extension of this quote from my Vita-Saw article: “The Vita-Saw somehow doesn’t appeal to any crowd. Perhaps it’s the constant downside forcing you to wonder after every close death, “Would I have survived that…?” Perhaps it’s the fatalistic attitude it implies on your own life; by equipping this saw, you’re admitting to yourself that your favorite contingency plan involves your own death.” In the complete other direction, the Amputator is for the Medic who values his life over even his combat/Ubercharge capabilities. When I die holding any other melee, I have to ask “Would I have survived with the Amputator?”
And I haven’t even mentioned the area-of-effect heals! While admittedly it is an extremely situational ability, it’s still a powerful one, since it outheals the Medi-gun and you keep the extra +3 hp/sec regen. One situation where I often bust out the Medicating Melody is during what appears to be a successful final push with teammates; at that moment, assuming I don’t have an Uber prepared, it becomes more important to have as many healthy teammates as possible to push the cart those last few inches or capture the last few slivers on the point.
Also, as I mention in this article, the Ubersaw seems to get me killed by encouraging me to whip out my melee and go to town. Removing that option and forcing myself to run for cover has traditionally kept me from killing myself in the name of extra Ubercharge.