lineupandwait,
To do the instrument rating you still need 5hrs night command, which alot of flying schools send students for 5hrs of night circuits.
The topic of wether or not to do the rating also comes down to what you want to do to build hours after your CPL. If you are going to become an instructor then I suggest you do the NVFR. If you don't you can still teach night circuits with a valid instrument rating. If your prepared to go bush to get charter then skip the rating and go straight to the CIR.
Just my two cents worth. Hope it helps.
BUGS