hmmm...
yes, you should care
no, you don't necessarily need to bother
the ORP, or OXIDIZATION/REDUCTION potential of a system-is a general indication of which of the two directions (oxidizing organics, vs. reducing them) the system is more biased towards
it's connected/related to the dissolved O2 levels (but not JUST the dissolved O2 levels), and can indeed be valuable REGARDLESS of ozone shmozone usage-it's not merely a controller parameter
the best 'use' of orp is generally trend indication-for example-if a system runs at a baseline level of 320, and one day drops to 270-you have a 'warning light' that someting might be going on in the system to tilt it in the direction of favoring a reducing environment (many anaerobic bacteria are reducing bacteria, iirc)
i've seen plenty of awesomely healthy tanks w/crappy redox levels, and plenty of sickly tanks w/'good' redox levels, so, as indicated by the others above as well, don't fret about it too much
conductivity, sg, salinity are ways to differently measure the same thing
oh, ozone can be run w/out an orp controller-just need to be careful about it-very careful