If it one addon to Unity3D you should get then this is the one.
Why?
Well it does help you with alot of things that make it so much easier to to.
If you use android then Playmaker is awesome.
Just to deal with touchscreen just in code in unity3D is a pain in the ass, but with playmaker you just add a FSM for the thing you want to do and it works.
The hardest part is to learn and think in state instead of code.
Im a old coder and thats my biggest problem with Playmaker is to adjust my thinking.
Right now I also have a big issues with a function in Unity3d 3.4 and using Playmaker do solve this issues.
Sure 100$ for an add on can be much of you have a very small budget like i have, but in the end I think it will payoff.
I can do stuff faster and better when i have learned to use playmaker and that will make my games better.
So it will cut my time for making games and it will have less bugs.
Also one BIG benefit with Playmaker is the people here that will help out if they can and the creator of Playmaker that do give you top support and try to solve your problem.
So the support of playmaker is very very good and playmaker do grow and soon you can make whole game with it without any problem.