If you're too busy to read the whole thing, I've summed up, sorted, and simplified some of the new stats.
Multi-class
Panic Attack
50% switch speed
50% more pellets / closer you are more max damage / spread is fixed unless you land shots, making spread less.
30% over all less dmg
Spy
Ambassador
First shot is no longer completely accurate. Long range capabilities nerfed.
Dead Ringer
Ammo kits and dispensers no longer refill the Spy's cloak meter
Your Eternal Reward
Can disguise with it now.
Added: Non-kill disguises require (and consume) a full cloak meter
Backstab-based disguises are still free
Reduces cloak duration by 50%
Scout
Sandman
Only slows alt-fire struck targets. No longer disarms.
Max ranged balls do 50% more damage.
Max range for balls are 20% less, but fly with original trajectory and speed.
Ball regeneration time 33% faster. (15sec to 10sec)
Bonk! Atomic Punch
Apply a slow effect to the player after phasing wears off, based on the amount of damage they absorbed
From -25% at low damage, to -65% at 200+ damage
Lasts 5 seconds
Pretty Boy’s Pocket Pistol
+15% firing speed
Up to +7 hp per hit (from +5)
-25% clip size (9 shots)
Crit-A-Cola
Each attack while active adds Marked-For-Death debuff for 5 seconds (does not stack)
Removed: Marked-For-Death when effect expires
Removed: +25% move speed bonus
Removed: +10% damage taken penalty
The Atomizer
Triple-jump is now only possible while the bat is out
Removed: Self-inflicted damage when triple-jumping
Removed: Attack speed penalty
Added: Melee attacks done while airborne mini-crit
Added: 50% deploy time penalty (to prevent quick-switch by-pass)
Reduced damage penalty vs players to -15% (from -20%)
Flying Guillotine
Removed: Crit vs stunned players (since sandman doesn’t stun anymore)
Removed: Mini-crits at long range
Added: Long range hits reduce recharge (by 1.5 seconds)
Distance considered "long range" reduced by half of the previous value when determining mini-crits
Soldier
B.A.S.E Jumper
Reduced amount of air control while deployed by 50%
You can only deploy parachute once until you touch the ground again.
Mantreads
The second least-used item in the game.
+75% push-force reduction from airblasts
+200% air control when blast jumping
Sniper
Darwin’s Danger Shield
Counter ranged burn attacks (e.g. flares), and strengthen melee fights vs Pyros
Afterburn immunity
+50% fire resist
(It actually said nothing about sniper vs sniper)
Razorback
Added: -100% overheal penalty
Added: Shield regenerates after 30 seconds
Medic
Vita-Saw
Melee strike people to get “organs.
Organ saves post death uber 15% uber per organ. Stacks 4 organs at 60%
Crusader's Crossbow
Landed shots now out-heal medigun. More health someone has, less uber is returned (like normal medigun).
Heavy
All Miniguns
Only during the first second of a fully spun up minigun do you have damage and accuracy lost.
Mini-gun no longer suffers damage or accuracy loss when you stop firing while minigun is spun.
Gloves of Running Urgently
While active, lose 10hp/s. When re-holstered, regain 10hp/s. (properties like drowning).
Constantly switching between gloves and other weapons causes higher hp loss rate.
No more mark for death. No dmg penalty.
Eviction Notice
Same principle as gloves when it comes to active health loss, but only 5hp/sec.
No more dmg penalty.
Fist of Steel
40% overheal reduction while active
40% healing rate penalty while active
Engineer
Rescue Ranger
Ranged repairs now consume metal (at a 4-to-1 health-to-metal ratio, e.g. repairing 60 damage costs 15 metal)