I've been to KK last year. Honestly, can't imagine staying there for more than one night - as said - drab, horrendous traffic (20 min to travel 500m), noise and pollution. Don't expect any vibrant clubbingg or restaurant scene either.

However if you get out from there and go explore Mount Kinabalu and surrounding park, other parks and tip of Borneo - you are looking towards to have good time.

Last words of caution - December is wet season and expect that every day it will be raining 6h.