I don't mind it, here and there.
Someone mentioned #16 at Desert Forest, which is an example of a good one. Someone brave can hit a big drive and get a big kick off the downslope of the hill, but but while that's already tight, the big tree in the left of the fairway makes it a very difficult drive. But if you pull it off, you can easily reach the green of the par 5 in two. If you try it and end up too far left, the penalty is not so terrible. You find a way under or around the tree and you should still have a wedge or short iron to reach the green in regulation. If you lay back, the tree provides similar thoughts for your second shot, in terms of going over, under, around, etc.
There was some discussion on the boards recently of a Denver course called Green Valley Ranch that has multiple holes with trees in fairways. #16, which has basically a whole grove plus a creek on the other side, probably doesn't work. There are options for playing the hole, but it's a bit much. The par 5 #2 has two trees.The first is in the right center, at about the end of the driving zone. It's where a big hitter would love to hit his drive. The tree forces that big hitter to challenge the left side, where there is a bunker. If you aren't hitting a huge drive, the tree isn't a huge issue simply based on the alignment of the fairway. Then there's another tree in the fairway some 50 yards or so short of the green. The hole offers enough angles that you can actually play into the green from right or left of the tree without having to go over it. If you are confident in getting the ball airborne, it's also very possible to lay back and hit a full wedge shot right over it. Having both trees there is a bit much, but I think the hole is still quite playable.