I frequently import from the states. USPS,UPS and FeDex all deliver, though I wouldn't recommend the latter as they have stuffed every delivery they've made to me.
Providing the parcel is less than a certain size, USPS (US postal service) has always been reliable for me. Most retailers include the option and you can get details on rates from their website. Another advantage to items that are posted is that they are delivered without any further payment being neccessary. All couriers will charge for fees if you live outside their "delivery area" (which seems to be about 100metres from their depot!). They will also charge about $100 dollars, on top of the GST, to clear the paperwork.
Telescopes and parts do not attract import duty, but are subject to 10% GST on items over AU$1000. No reliable retailer is going to fudge this for you, so don't even try!

Get your vendor to separate the cost of postage though as it's not subject to GST or duty, and if you've already spent $1500 dollars on a 10" SCT you don't want to pay on the extra $6-$700 it cost to post.
One of the main things to be wary of is getting a crap example of your product. This happend to me with my first Tak TSA. It had clearly been mishandled and was badly out of collimation. What it cost me to send it back to the retailer and then bring it back here, quickly ate up any savings I made on the o'seas purchase. Trust me though. You really DO want a local warranty on anything more complicated than an eyepiece!
With that in mind, with local prices falling as the $ rises and unless the product is unavailable here, I would stick to small items that cost no more than $50 - $75 or so to post.
There are obvious exceptions, like Meade or Celestron SCTs which are grossly overpriced in Australia. Sometimes by as much as $2000. But get the overseas retailer to check it out first and get a certificate of inspection.
Buying 2nd hand from a reliable source off
Astromart or
Cloudy Nights is also a good way of saving cash, but quite a few of them are very insular and won't post o'seas.
I've never used a freight forwarder. Their main
raison d'etre seems to be taking care of the paperwork, which is actually fairly simple. Of course they charge a fee for this and to deliver your item. Unless you are totally unwilling to fill out forms or the forwarder takes responsibility for the condition of the item, you can probably save up to the cost of a good EP by doing it yourself.
Hope this was useful.
Good luck with your purchase.
Peter