I hiked the Georgia Pinhoti shortly after Snake Trail Race, a big MTB race held in January, February and March on the Pinhoti. Sadly, as a result the trail was full of litter. The racers had just tossed the packaging of their energy gels and other garbage. But I also met one of the race organizers who was already cleaning up after them. I met a lot of bikers on the Georgia Pinhoti and strangely enough most of them at night when they were training for the next race after work. Most of the Pinhoti is on single file trail and I felt really threatened by some bikers who came racing down the trail. I had just seconds to jump off the trail and let them pass. Still, trail erosion due to MTB use is minimal on the Pinhoti.
But I must say that the Georgia Pinhoti is really geared towards cyclists and not towards hikers. Trail crew remove any obstacle from the trail like blow down trees so that the cyclists can pass. There are no shelters on the Georgia Pinhoti because the cyclists don't need them. I wondered about that bike orientation and asked the president of the Georgia Pinhoti about it whom I met on the trail doing maintenance. His answer was very surprising: Almost all Georgia Pinhoti Trail volunteers are bikers. Hikers in Georgia tend to volunteer on the much more popular - leaving only MTB people to work on the Pinhoti. And these of course form the trail according to their needs.
Overall the MTB's did not spoil the hiking experience for me, but I still prefer the Alabama Pinhoti that is 100% geared towards hikers.