Welcome onboard, Les..!
A few things.
Firstly, give yourself a little time to get used to using the lens - many people find that there's a bit of a learning curve to using IS lenses. It's worth the effort.
As Rob say, the image in the viewfinder will jump about then suddenly "settle" - it's very cool.
Even with IS, you still need to develop a decent handholding technique (which is actually very straightforward) - this is an excellent tutorial, and I can confirm that the advice in it works:
http://www.nikonians.org/html/resources/guides/technique/handholding1.html
What settings do you have the lens on? Make sure it's switched on!
Re: the weight, I'm not a big bloke, but I can manage the lens for a whole day (and a rucksack full of what I need for a day out) without much trouble. You get used to it.
It's worth buying a broad neoprene strap though - I recommend the Optech Professional:
http://www.warehouseexpress.com/index.asp?photo/camstraps/optech.html
Last thing - IS and good handholding technique are great, but as the article I linked to says, it's always worth bracing yourself against any available support like fence posts, railings etc - every little helps.
But most important of all - persevere.