For a truck, I think these handle great.
They have a pretty simple suspension, with IFS being the only real "bell or whistle", yet they are very predictable and accommodating.
The ride is an excellent compromise between plush, planted, and capable of carrying weight.
My previous car, for example; if I'd put four adults in it would have immediately handled like a pig. In the 4runner, while the extra weight is noticeable, it is manageable.
They also seem to handle modification (different spring heights/rates, shock valving, tire size/weight, etc.) as well as any vehicle I've experienced.
I put this down to Toyota not speccing super cheap parts, especially when it comes to things that can't be easily replaced, and doing a very good job of learning from their previous vehicles. Of course, this is one reason why these were relatively expensive compared to the competition when new, especially in light of the feature list.
In the long run (14+ years for me) it has proven worth it.