as someone who runs several 200 tick servers, i feel like there's a lot of misinformation going around about higher tickrate in tf2.
tf2's engine is locked to 66.67 tps, and when you "unlock" it and go beyond that limit (with twiikuu's metamod plugin or otherwise), things do start to break.
higher tickrates cause wallbugs to become more frequent, essentially meaning that you stick to diagonal walls at high enough tps.
higher tickrates *do* also affect projectiles, but as far as I can tell, the only projectiles that are actually changed in any meaningful way is demo's pipes because rockets, arrows, and even the stupid little wrap assassin ball thing (that randomly breaks on the sides of visleafs sometimes) all have a fixed speed (again AFAIK, might be wrong).
ramp sliding is also broken at higher tickrates, but this can be functionally fixed with a sourcemod plugin called groundfix, developed by jumpers/surfers (god bless em):
https://www.youtube.com/watch?v=7DiM0llQOZM&feature=youtu.be
people have complained about sentries firing faster or doing more damage, and even if that were true (which it isn't, I've done tests on my own that debunk this) it could be fixed by setting the hidden cvar
tf_sentrygun_damage
to a lower value
the "shutter problem" where shutters break sometimes has been fixed as well with twiikuu's plugin as well.
buggy dropped weapons can be disabled with
sm_cvar tf_dropped_weapon_lifetime 0
and dropped hats off dead players could be easily fixed with another sm plugin.
there is obviously increased CPU usage with higher tps, and i very much doubt that arie @ serveme would want to implement it for free or that NFO/Tragicservers would want to implement it across the board for the same price they currently charge for servers.
but, gameplay does feel significantly smoother at higher tps. ping becomes almost a nonfactor, from what i've heard (and experienced). 60 ping feels like 10 ping, 30 ping feels like LAN, etc. soldiers become much more powerful because of increased air-control, medic's arrows don't randomly not register nearly as often, melee actually works, etc. etc. etc.
all in all i genuinely believe higher tickrate in TF2 is an upgrade, even with the downsides, which could probably be remedied with plugins. sorry for the nerd essay!