Weird hitboxes, invisible trunk parts, magnetic branches that stick to any frontloader tool in the vicinity, inconsitent weight (I can carry half a pine, but not a birch twig?) The pines/firs aren't that bad, but the leafy ones are a nightmare. It feels like using one of those claw crane arcade machines that can barely hold on to a plush toy lifting anything heavier than that just causes the claw to flop impotently and drop everything. I hate the new control scheme as you have a lot less control, especially of the outer boom, but I guess I can get used to that. Working near a pile of wood/limbs is a nightmare as random pieces of wood keep sticking to the tractor/skidsteer and/or the attachment. They seem to have been converted into powerful wood magnets. Oh and who holds a chainsaw that far out! Delimbing is very hit-and-miss and I usually have to do several passes at different angles. Audio stops while cutting if you move too much or cut too fast. Cut marker appears nowhere near the saw (looks like you have to aim with the center of your screen, not the saw). It was perfectly servicable in FS17, I don't understand why it was changed. I suspect the changes were meant to fix some issues, but as far as I can tell it's mostly gotten worse.
Forestry has always been a bit wonky but I feel like there are some changes in FS19 that make it a lot worse.