several things i've seen that you need a strong guarantee on from the installer...

1 - roots and weeds.... make sure the weed barrier or ground prep removes everything that could possibly grow under the turf (carpet). i've seen a couple of installs where something started growing that causes a 'spike' in the turf. the only way to fix this was cutting the turf to get to what was underneath. dave pelz has many of these issues in his backyard...

2 - seams. over time, the turf will begin to pull. you need to make sure the seams are well done. or make sure the installer will come back and repair in the future if the seams start to separate.

3 - color of the turf. my turf is synlawn, and is guaranteed for color for 10 years. in the texas sun, most turf will start to fade. make sure you know how long the original color will last.

4 - make sure you understand the 'stopping' ability of the turf or the install. my green is pitched slightly from back to front to allow a shot to 'stop'. most flat greens will not hold a shot. my green also has a layer underneath the turf called 'shotstopper' which contributes to the green 'holding' a shot. I have a buddy in dallas who didn't address this and his green will not hold a shot. so its limited to chipping and putting. you can actually back a balll up on my green if hit properly with spin

all i can think of for now...