My parents did rubber mulch in the kid's play area - she does in-home daycare, plus for the grand kids. I talked to them about it because I was thinking about doing it around our playset and some other areas in our yard. I decided against it.
This is from a point of view of kids playing or people walking on it.
Pros
1. Never have to remulch and it hasn't lost it's color in the 4 years they had it.
2. Much softer for the kids to walk and play on vs wood.
3. Expensive up-front, you'll quickly save long term.
Cons
1. Dosn't retain water, so if you're doing around landscape, it won't retain water for the plants.
2. It does get a little warm in the hot summer months. They hose it down to cool it down.
3. It stunk for a while.
4. They expanded the play area and when they tore up grass around it they found a bunch of ground up rubber pieces, more than likely pieces that flew out and mowed over or tiny pieces that got knocked/blown over into the grass.
5. It blows around and moves around pretty easy in the wind so it mounds up and they have to re-flatten it.