hi, we moved here oct 2008.
i just went through yellow pages & picked out some of the bigger co.s most of them INSIST that they pack - so that they know what it is. there are some things you just can't take - NO alcohol, no foodstuffs, no liquids (this includes things like kids paints, biros etc, no flammables (inc all cleaning things, spare house paint etc), and no soil - so go through garden eqpt & clean it all thoroughly just before the actual move.
tbh, it wasn't much worse than moving from one town to another - once you have to pack it all up & put it in a box, it doesn't matter how far that box is travelling.
it will take about 6-8 weeks to get there, depending exactly where you are, and can take up to 2 weeks to clear customs.
ask the person giving the quote about how often they sail. if dh's co. is paying, make it clear that it Is only a quote - fuel charges went up massively as we moved, and the cost of shipping was rising by the week.
ditto what kansas mum said about insurance.
US unpackers don't actually unpack - they just deliver boxes to the right room (maybe). keep all the cardboard boxes - they're not included in a house move here, so when you leave you have to buy/provide your own. we have a cardboard box room in our basement, where we flat packed loads of them.
good luck!