"I like it mainly because it will hopefully force spies to be less like James Bond, going solo and trying to do everything themselves, and make them more reliant on their team."

That's a problem of people not understanding the capabilities and limits of their class. Making them slightly worse at it won't teach them anything, and weakens the class for the wise players.

"But a smart engy should need to be beaten by a sapping spy backed up by a combat class. Essentially, the sapper is to keep the gun from firing while the solider/etc takes it out."
"nothing annoys me more than a single spy trying (and failing) over and over again to sap my sentry to death. If he would just wait for one teammate to back him up, he could actually make my life difficult."

What teammate to back him up? In an imaginary wonder world made of brave players who have a plan, that can work. But my experience speaks that people in general will not push forward against a Level 3. They just won't do it, unless it's Dustbowl III and that's the only thing they can do. They'll get close, they take a futile pot shot, then they'll see a pyro somewhere and go kill him to score a frag. They won't watch for gun breaks on the scoreboard, either. But when I break guns and announce that they're broken, suddenly everyones' heads become full of eyeballs and they go marching in. When your team just frags around waiting for the spy to break all the guns and clear all the snipers, needing even more alone-time with a gun to break it does nothing but hate on the player who's trying to help his team make a move.

Finally, while I've heard many people (excluding myself) complaining about failed backstabs, goofy frontstabs, and getting stuck when decloaking, I've never heard anyone say that it was too easy for a Spy to break a gun by:
1) Sneaking in.
2) Catching an Engineer off making a sandwich.
3) Getting the sapper on it.
4) Not getting wrenched.
5) Shooting the gun.
6) Four times.
7) Without getting wrenched, pyro'd, demo'd, or crit rocketed.
8) Optionally escaping.

So how much is this "slightly less?" Five bullets? All six? Will I need to reload? I don't have time to reload, I've died plenty by going after an L3 with three in the Taurus because I don't have a second and a half to spare. Gunning down an L3 is not a fun job as it was.


What more can I say... they're fixing what isn't broken, and meanwhile I can't stab at someone without it not registering, me getting stuck to them, and eating rockets.