Dean,
I've also used them for several years and had no major issues.
Just another couple of points to be aware of, as the others have covered the "In Stock" vs "Available" thing.
When you complete your order, you have an option to ship the complete order or split the shipment and ship what's available. Always select the option to split the shipment. Should any part of your order actually be unavailable, they will ship what they have and the outstanding item/s later. You will not be charged additional shipping.
If paying by credit card, you will be expected to pay the full amount up front before the order is processed. I don't find that a problem, as you are committing the funds anyway, but some people have an issue with that (they expect the CC to be charged when they actually ship the items).
Average shipping time for "air mail" items is about 7 days to Sydney.
I've also used HLJ and their service is good, if a little pricey but often that is unavoidable for hard to find items. Always check their "specials" page, you can often find some nice bargains there.