I just bought an octave mandolin while on vacation in Western Canada. It's a very pretty, well-made instrument, made by a luthier in Saskatchewan, and sold by Lucky Star Guitars in Lethbridge, Alberta. Now I'm playing the mandolin tunes I know on this new instrument, and loving the richness and resonance of the bigger instrument.
You won't regret your purchase, Colin. The octave has a rather special voice, I feel.
Yes, there's a greater tendency (on my part at least) to play more open strings and let notes ring longer (instead of stopping them, which I would tend to do on the mandolin), just to revel in the rich overtones. And, of course, chords sound fantastic! I don't have the proper string set on the instrument yet, my G strings are too light (0.42s). Also bringing the instrument across Canada from the semi-arid West to the humid East (where humidity has been between 65% and 85% this week) has had an effect on the instrument. I humidify in the winter, but don't de-humidify in the summer.
If you want a heavier string set try D'addario J76 mandola strings - the bass course is .049. JT76 (Flat-tops) also work well - same gauges. If you prefer Flatwounds there's a Thomastik 174 set - but expensive.