Believe it halves the theoretical bandwidth. A reason to avoid having it enabled unless you really need it. A wired AP can theoretcially provide a possible 300Mbs to it's clients whereas a meshed one only 150Mbs (please correct me if I'm wrong someone)!
Reduces WLANs per WLAN group from 8 to 6.
Reduces max possible VLANS from 256 to 192
To remove Mesh also requires ZD reset to default, in other words back to square one.
Problematic if you thought it was a good idea to enable it but didn't really need it. You can disable it on the APs but it will always remain enabled on the ZD until a default reset.
So think before you apply..