I wouldn't put it in a backyard.
For it to be safe, you need to have a layer of insulation or padding under the grass. There's a dog park in a nearby neighborhood that has artificial grass just tacked on over plain concrete and it is absolutely not safe for the dogs (or for the people who have the misfortune of slipping and falling on it). They can't get traction and I'm sure it is not good for their joints to be jumping on that, because there's no cushioning for the impact.
Many trial facilities, especially agility venues, have properly installed artificial grass over a layer of matting or plastic granules to absorb impact. That seems to work much better. However, keeping it clean is very important -- dogs are strongly discouraged from urinating on the surface (and some facilities will charge you $5 per potty mistake to cover the cost of cleaning and eventual replacement) and you can't eat or drink on the turf because if something spills and soaks through the grass layer, it's never coming out.
I can't see how you would keep the turf clean in a backyard (all the agility venues I've ever seen with it have been indoors) and I think it would be pretty expensive to install.
ARCHMX TDCH Pongu the Insane, CD-C, RE, RL1X6, RL2X5, RL3X2 (GSD mix, b. Apr 2010)
Crookytail the Tigerwuff, RL1, ITD (Akita mix, b. Jan 2011)