I hadn't played for quite a few months before the update (or realistically for well over a year if you don't count reinstalling for like 2 days). It's been just about big and interesting enough to get me playing again for now, but also jank and head-scratchingly executed enough to already have me a little frustrated again.
I'll spoiler my long-ass thoughts on individual changes so they don't take up too much space in the thread for people who quite justifiably don't care about the opinions of a dude who hasn't played 6s since 2015.
Thermal Thruster feels like a meme that's one or two changes away from being really good. I don't think fixing the damage to players you land on so that it actually works will be even close to enough but it'd be a start. It has to at least either draw or holster faster – not even necessarily both, but definitely one or the other. For a mobility tool that uses up a secondary slot I think you really need to be able to either reliably engage or disengage with it, the obvious comparison being Gunboats which allow you to do both, and right now it's so slow to switch to and from that you can't really do either with it. Even with the Degreaser it still feels pretty slow and with that you're gimping your damage output even harder. Better air control would help too. Overall the whole item just feels very "canned" – it takes an age to switch to, does the weird hop before the launch, doesn't let you strafe properly and then takes another age to switch back from. Doesn't fit into the flow of combat at all.
Gas Passer doesn't feel like it has a niche. You throw it into a chokepoint and then what? They walk through it with heals and don't really care about the afterburn? They uber through choke and it does straight-up nothing? The rate at which you actually get access to it after spawning is in the same kinda ballpark as the rate at which uber builds and the usefulness of it isn't even in the same stratosphere. Besides all that, Pyro already has a strong chokepoint lockdown tool with airblast, feels a lot like diminishing returns sacrificing other secondary options for even more (and arguably less effective) area denial on top of that. I guess you could throw it onto point after they've gotten through choke and that does something maybe, but good luck building full meter before they push. I don't even know where I'd start with suggestions for it because the whole concept feels redundant.
Slap Hand was designed to be a meme and accomplishes exactly that and nothing more.
New fire particle effects feel more dense and visibility-impairing than the old ones, you really can't see shit past them at all sometimes, especially with multiple Pyros knocking about. Not a fan.
I really wanted to like the new Mantreads but rocket jumps without Gunboats just take so much health that you can't properly exploit the effects without the Rocket Jumper and then you're just playing a meme loadout anyway. Maybe they'll be good for pockets who don't want to get juggled but unless Pyro really does make it into the meta full-time somehow I don't feel like pockets really benefit in some huge gamechanging way from increased air control, so for that purpose they're essentially the same as they were before the update anyway. Legitimately laughed out loud when I saw that they buffed the Cow-Mangler, that part of the patch notes should really be accompanied by the Seinfeld theme.
I feel like I would like the new Pocket Pistol a lot if the +15% firerate actually worked, as it is it feels underwhelming. The new Flying Guillotine is dope and I like that it's not pigeonholed into being a Sandman combo anymore.
I kinda dig that burst-fire Heavy is a proper thing now. Makes him a lot more enjoyable to play at the very least. GRU and Eviction Notice changes are really interesting now the HP-stacking exploit has been fixed, being able to do a reasonably fast Heavy-to-mid with the tradeoff of showing up with about the same health as a Soldier is a compelling idea. Kinda funny that it feels like Heavy got more sensible, thought-out and potentially healthy changes than Pyro after losing the vote.
Not sure about the Panic Attack. The switch speed is nice but it doesn't really feel like it does damage. Kinda gimmicky still.
I'm not sure the Ambassador really needed the change but at least they listened to reason and implemented it in a way that doesn't introduce unnecessary RNG.
Speaking of unnecessary RNG, I know they're most likely not gonna get rid of random crits on casual servers. I really think they should, but I can understand that it would be a big leap to remove a fairly iconic feature of the casual TF2 experience. But for fuck's sake, at the very least they could finally get rid of random bullet spread. Shotguns on random spread servers feel awful and it benefits literally nobody, even the casual players who "benefit" from random crits by getting lucky kills will get hindered just as much as helped by it.
Don't think I really need to say much about all the bugs. Really siding with all the people here who think that over 400 days should've been enough time to have launched the update without so many gremlins. Some bugs you can't really see coming, sure, but then there are things like the jetpack not even having its listed damage effect which you'd think competent playtesting would've picked up on.
All-in-all I'd say it's cool, but for how long it's been you'd really think it'd at least be a more polished experience and you could even make the argument that, while the foundation has definitely been laid for Pyro to be a much better class, they may not have even accomplished the main thing they set out to do and really done it. Time will tell on that I suppose. I kinda feel like they hit the bare minimum standard for the update to not be outright disappointing for the time spent on it.
Boggles my mind that Valve don't apply their usual strategy of outsourcing everything possible to the community and bring the TF2 Beta back – sure, it won't get them a lot of feedback, that's been shown in the past, but it'll certainly get them some very important feedback and playtesting from the people who are dedicated enough to the game to care. Quality is much more important than quantity when it comes to that kind of feedback anyway I'd argue. Just have the option there and at the very least a handful of knowledgeable, dedicated people will use it and hey, what do you know, now you don't have to spend quite as much extra time after an update doing retroactive quality control anymore.