We lived in Sydney for the later six months of 2003.
As part of our last trip we deceided to visit Featherdale on a reccomendation from an Australia travel book. And what a great suggestion it was. We stopped at the wildlife park on our way up to the Blue Mountains. We rode the train with a medium sized suitcase each and had little to no difficulty getting around. We got off the train and took a city bus that dropped us off at the enterance to Featherdale.
The people at Featherdale were very kind and accomodating. They allowed us to store our bags in thier office while we visited the park. The whole park is very quaint but with tons to see.
The visitors are the ones who are restricted in some areas, the animals have freerange. Kangaroos and Wallabies hop about and lay around anywhere and everywhere. You can buy inexpensive cones of food to feed them and anything else that comes around you. They have several pens of koalas that are so intimate (in a not-too-small-for-the-animal-but-good-for-the-visitor way) that a koala nearly lept onto my fiance when it was going for the pole next to him. The caretaker then took the koala back to the 'tree' and gave it more food. We were able to pet and take pictures with a koala for free, but we could not hold one. It is illegal for a non-caretaker to hold a koala in NSW. They have a non fenced in area with several kookaberras. In fact they often get out an just hop around the grounds (thier wings are clipped). There are Many different animals there that you can get very close to.
We went at the beginning of summer and there were people there but not crowded at all. The price isn't bad either for what you get. Adults $18.50AU, Kids 15 & under $9.00AU. They also have student, senior and family rates.
Our whole experience there was amazing. We left the park just just in time too. After spending about 2-3 hours there we caught a bus back to the train station. On the way back a Huge rainstorm suddenly pounded the bus. I was excited, it was pretty crazy. We then witnesses for the next 20 minutes, the loudest thunder I have ever heard! It was so loud you had pause when talking to the person next to you. I love thunder!

The Featherdale website is also very informative:
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It's possible to visit here using public transport. You will get more time than you do with an organised tour.

There are lots and lots of animals here. It is great spot to just watch the animals.

It's quite a basic spot but has a huge variety of aussie wildlife.