Since people have chosen to ignore the bulk of the PBE changes.
Marksmen changes: Base AD up 5, AD per lvl down, equaling out to around -5 from live at lvl 18.
Item changes:
% pen changed to bonus pen.
Typical tank Ar around 170 mid game.
41% ArPen vs 9% +40% bonus pen
S5= 100 effective Ar
S6= 110 effective Ar
For clarification, that 10% effective Ar means an additional 10% effective health. Taking a 4000 effective health tank to 4400 effective health.
From 80 to 65 AD
From 8% to 6% current health.
From 80 to 75 AD
From 80 to 65 AD
From 60 to 55 AD
From 80 to 75 AD
From 30 to 25 AD
>Marksmen get more crit now.
You want to know the bright side of this?
A. More stable DPS.
B. Less AD means crits are less bursty.
C.
D. Hitting 100% crit means giving up on one of the following: sustain, penetration, boots, defense.
For all the great new utility they are getting, we are getting some MUCH needed changes.
Not to mention, Jungle is getting some MUCH needed love with the new starting item and warding upgrade.
>Insert item is more expensive!
Meanwhile gold generation is up, minions spawn sooner and gold from jungle camps is up. So far the game is actually speeding up as jungle and lanes are getting more gold and building faster than before. Expenses be damned.
Tanks are buffed, mages are left about where they were, meanwhile Marksmen are getting some much needed changes that may make the class more interesting and less about rushing 
Is there likely going to need to be some more tweaking? Heck yeah, you never know just what is going to be broken until you mass test it. A few thousand testers on PBE are nothing compared to the millions of people on live. But for the sake of Ionia, don't freak out without grasping all of the facts.