Hmm... Because now spies actually became a force you must reckon with instead of the poor guys who were bumped into and immediately shot or burned to death and who had to rely on sapping teleporter entrances at spawn to boost their score?

Not really a force to reckon with tbh, just the fact that they are the only class to know how low health you are and they have the accurate revolver which you can snipe with means that they are powerful in the wrong way (A non-spy like way).
I have played spy before the update, and I could easily get a 4 kpd as spy by just using the revolver, disguise and cloak, now that you can see health means you can target specific people in a croud, while you team mates spam in, and pic off low health people, even better than a sniper. Or you can wait near the big health packs, check peoples health as they go towards it, and just pick off the ones on low health, leaving the high health people alone. Revolver is in no way underpowered (it's not overpowered either).
Give them longer cloak, +50 health while cloaked, which when uncloaked is degenerated over 10 seconds. I don't care what, just not the overpowered thing it is now.
Have they fixed facestabs? That hasn't happened to me in a long time.