Let me give you some background on my boy (this is our first Golden and I'm not sure how 'typical' he is). We adopted a rescue Golden about 4 months ago. He was 15 months old when we got him and was EXTREMELY mellow at first. He was severly neglected at his original home - they had him outside in a small pen 24/7, never cleaned the pen out

, never gave any attention and definately never bothered to teach manners or basic training (WHY some people get a dog is beyond me, but that is another subject for another day

).
I think he was forced to 'grow up' a little sooner than most (I've heard puppy stage lasts up to 3 years

) and thought he would stay mellow. Well, Riley has adjusted pretty quickly and I have been told that he is now behaving like a 'typical' 1 1/2 year old Golden.
At 70+ pounds, he can be a bit rough when playing with my 6 and 3 1/2 year old girls. He LOVES their stuffed animals and I go through chew toys like they are going out of style. He chases my 15 year old cat around and to top it off, the poor dog has allergies so he gets an antihistamine 2x a day. We are currently going through our SECOND obedience class (remember, we've had him for 4 months

) - the first was very 'old school' - which I didn't particularly care for - so I now have him enrolled in another school that is much more positive reinforcement oriented.
That said, I absolutely adore him. My 3 1/2 year old dd can just collapse on him and he doesn't blink an eye, my 6 year old plays 'school' in her room (he's the student) and he lays there and deals with it. And I'm sure that we'll get past his manners issue with a little persistance and time. He is a big baby who really just wants to be loved and adored all day long. I'm a Golden convert now.
I highly recommend a cage, PLENTY of chew toys and obdience class - absolutely!! If you like dogs, you'll love a Golden.
I know this was much longer than you wanted or needed, but I absolutely love my boy!!