Unless this is your first time moving abroad or looking for work, I wouldn't bother with BUNAC's services if you're a native English speaker. Everything they offer can be easily done yourself.
The visa application itself is very easy, no need for their guidance on that front. Getting your TFN number (for taxes) is a simple form. They delayed my number for a while because the woman at the office wanted to "check with me about something" and insisted I come back to the office to talk to her. She wanted to make sure I was legally married and submit the application properly in front of me so she "doesn't mess anything up." She only knew I was married because it came up in a casual chat! No where on their paperwork did it ask if I was married, and I assumed it was irrelevant.
The first-days benefits went unused because I was not allowed to add on a second person (my husband) to my airport shuttle reservation, nor upgrade my room type at the hostel, or switch it to another time/location.
The SIM card went unused because they give you the most expensive cell carrier in Australia-- $20 more per month! It's better if you're out on the farms, but I wasn't going to do that.
I booked knowing I wouldn't use many of their services, but I knew I wanted help getting work, from both their jobs board and their employees.
As for the job board, it's nice, but it's riddled with omissions. Many listings say "email your resume" only to have a phone number provided. That's because they lift the jobs from Seek, and Seek has an internal submission that they can't replicate on their job board. So I would be forced to call and get the email and I was never called back for any of those jobs because it makes you look pretty incompetent. (No, I tried and could not find the same listings on Seek itself.)
There are two women who are charged with helping us find work. They are both backpackers on their 2nd work holiday visa, and they're German and Italian. They're very nice and their English is good, but that's not what I was looking for. I wanted an Australian's perspective on wording choices in my resume, which was impossible for them to do.
In general, this is a good idea for non-English speakers who will have trouble navigating paperwork and visas because it's difficult in a second language. But if you speak English, then it's all very straightforward on your own.