This has been a very popular thread. I've come back to it every now and then and have always found new (and interesting) comments to read and think about.
Given the ridiculously high prices of 120 film in Australia just now, it frankly surprises me that anyone Down Under would still be shooting 120. A luxury, perhaps.
I see hopeful sellers trying to get A$10-$12 for a roll of 120 Fomapan on Ebay. One or two reputable OL film sellers are trying to keep their prices reasonable, but the bipolar up/down free-float of the Oz dollar is most likely defeating them. Also having to pay up to $15 for postage on a film order. One has to buy big (at inflated prices) or order from overseas. Two guess which option most 120 shooters I know, go for.
I occasionally buy 10-20 rolls from a Melbourne OL seller who tries to keep his prices fair, provides excellent service and is a truly nice person in every way to do business with. By agreement, as I live not so far away, we meet for coffee and I pick up my order. Nice and sociable. I am happier paying $8 for coffee than having to throw my money to Australia Post, and have a so-called overnight delivery service I pay good money for either turn up several days after or end up halfway across the country from its intended address, which then means a wait of up as long as eight weeks for some flunky to find the parcel, read the rules and regulations manuals memos and make a dozen phone calls until someone with half a brain finally makes the decision to fix the problem by returning the parcel to the sender, not the intended recipient (with my correct address always always on the front). Sadly, this is no joke. It happens to me a few times every year.
Inevitably, medium format shooting may be doomed to disappear in Australia, almost entirely due to high costs. Not many of us can afford to shoot B&W at a dollar a shot, or color at up to $2 and beyond. Pure economic madness, even suicide.
So for medium format in Australia, 645 seems the way to go. Fifteen or sixteen exposures to the roll makes sense. Excellent sharpness and tones. Easily processed. Rectantular images that print well on standard paper. Convenience of 120 or 220. Portability of the equipment.