As much as I like my new kit so far, I really wish the unlockables were restricted to fluff, like special taunts or skins (say, medals on your coat... something that wouldn't interfere with the overall gameplay).
TF2 is a great game because it is very accessible, even to new players, and emphasizes teamwork. With weapons being tied to performance-based unlockables, certain strategies (say, krit + a normal uber) are now a crapshoot, since you can't bank on someone having the right gear.
I won't be butthurt about it all... I'm just a little disappointed; I especially feel for the casual players and all-rounders. Hopefully, there will be a balanced system of allowing all the unlocks in-game without jumping through hoops.
And yeah, that ubersaw medic duo video is insane, but a lot of the enemies just stood around like idiots. A well-placed rocket/sticky would split up the pair , and you could pick them off one at a time (whenever I see an uber as a solly, I aim for the doc's feet asap).
Edit: Though based on that vid, I would not be surprised if the ubersaw gets tweaked to not charge while under invincibility.