Tree saddle pros: I think the biggest pluses is that you are always tied to the tree. If used properly it is almost impossible to fall with one. you can wear your stand into the woods, you can shoot a deer from any direction a deer will approach from. If you are doing a one day sit then all you have to do is spike a tree or use your Lone Wolf climbing sticks. No need to carry a lock on stand with you. If you hunt in a club with other people then just put climbing sticks up and no stand. Most people will not try to sit in your stand location without a comfortable stand on the tree.
Cons: I would not recommend them for all day sits. You can find some comfort but all day would be asking alot. I would rather sit in a nice lock on for long hunts. People with bad backs my have an issue with them.
A saddle will not answer all my needs for a stand but does give me an edge when I need one.