GWM isn't too bad right now. The -5 to hit is a pretty significant penalty that's pretty difficult for melee PCs to make up for, especially at low levels.
The Sharpshooter feat is going to be way worse when/if it's added. +2 from high ground when combined with the +2 from the archery fighting style almost completely nullifies the -5 penalty. It's essentially going to be a -1 to hit for +10 to damage which is absolutely ridiculously strong.
