Boring, obvious advice from someone who's been using Kubuntu since Feisty: if it's your main desktop, don't upgrade now unless you have to. For the sake of a couple of weeks' waiting you stand a much better chance of avoiding any teething troubles, or at least being able to to find documentation for your problem. This is especially relevant if you use a laptop or unusual hardware.

(For the record I've been hit with laptop wifi incompatibility (the Intel wireless driver got changed, config files didn't update) and software RAID in the GRUB 2 update.)