Don't fix it if it aint broken is my motto. 5.0.8 was working without any issues but we were getting left a little behind now 5.0.16 is out so were thinking of upgrading.
We picked 5.0.11 for the asterisk integration zimlet having read somewhere it worked well with 5.0.11
Asterisk PBX Integration Zimlet (new)
Will probably wait for 6.0 before upgrading again