I'm a Brit who now lives in Sydney, but also lived in Adelaide for 2 years and had DS there.
Spiders - I hate them, and we did used to get redbacks in the garden but they are slow and you just spray them, no drama at all. We got the occasional huntsman but very very rarely. Saw snakes when bushwalking but not in the back garden or anything.
I find Aussie mums to be lovely, friendly, inclusive people. No one cares if you breast or bottle feed, it's just not an issue either way. Very little judgyness in general. We do loads of outdoor stuff - just had 3 hours in the park today with friends doing some exercise and taking it in turns watching the children.
We swam outside in the summer, went to the beach, it's fab, really good for that.
Downsides - it's very expensive. Food is shocking after the UK, and it's hard to find good quality resonably priced clothes. M&S online is my friend! Also, it's a loooong way from the UK, and expensive to travel back. We thought we would be back once a year, but we just can't justify the cost - plus, there are lots of nice places to go over here!
Driving is a breeze, lovely wide open roads and even in Sydney it's totally fine.
Aussies I have met aren't rough around the edges at all, and I am far more likely to use casual swear words than they are.
You don't seem to get the same hoodie type gangs of lads just hanging around.
Mind you I have said all this about cash - but we are living in Sydney on one salary, with a rental property and a property that we rent out - so I could just get a job, but we have decided that we want me to stay at home with DS for the time being.
One thing about Adelaide - it is quite a small town and the reason we moved back to Sydney was that for DH, the jobs just weren't there. There are good jobs of course, but if you're ambitious and keen to get on (he is in finance) then you need to be in Sydney or Melbourne really. Oh and the shopping is dire. Which is good as you will need your money for food.