Firmware updates are released both to correct known problems and improve the cameras performance.
Whether you update or not is your choice but not updating means that known problems can affect your camera.
I've updated all 4 Pentax cameras I've owned including the K30 and never experienced a problem during or after the upgrade. I'm presently running K30 V1.05 without any conflicts.
I'm not saying you couldn't have a problem however if you follow the directions and
especially ensure you have a freshly fully charged battery you are more than likely not going to experience problems.
It may happen that the firmware upgrade will return custom settings to default but that only happened to me once or twice. I suspect that the firmware update corrected a problem that used the
custom setting.
Also note that
firmware V 1.05 includes all previous upgrades so this would be the only one you need apply.