I can only think of positives such as setting your 4runner different from all the "Mom takings kids to soccer game 4 runner." more than half of the people I see in 4runner are moms! Yish! High ground clearance meaning less likely to damage the body. More importantly, it's hell of a lot sexier with lift and bigger all-terrain tires. It's the cheapest way to lift your 4runner and only way to keep X-REAS intact if you have them.
Negative stuff: It'll be tough on your shock if you off road reguarly. A bit stiff ride which some likes since it'll drive like a truck and some don't if they have a soft butt. I used to drive a POS car with like no shocks, so it won't bother me. To me, it's all about putting more testosterone into the truck and makin it look sexy. Oh, and SOME Toyota dealers will give you sh*ts if you go in for some warranty repair.
It all depends on what your drivings needs are. But, I say go for it. Best mod for its money. Especially, if you're not an off-road addict. I got 3/2 cornfed kit on its way. I just need to find someone to install it in this asphalt hell region.