I did the Sun Seeker with sailing trip. Apart from the sailing, the trip was good fun. Mark Davies, our trip manager, was a really nice guy who seemed to genuinely care about all of the people on the trip. The accommodation was good, lots of high energy and scary extras (bungee jumping etc) if that's your thing! Plus a few more laid back activities for us non-daredevils. The Fraser Island trip was beautiful...basically it was a really great way to see a huge amount of the East Coast in a short space of time and make friends along the way.
And now for the bad parts... the sailing. It's pretty expensive and not worth it at all. My visions of luxuriating on the deck in the sunshine with some drinks, music and friends... nope. This is in fact a particularly scabby racing yacht. They pack 20+ of you in there. Way too many people for such a small boat. You're on top of each other and bashing your head/knees/elbows CONSTANTLY. Uncomfortable, stuffy sleeping quarters. You can't take a shower for 2 days. You can't go below deck when the sailing is occurring: you have to cling on to a piece of wire whilst the boat tilts nearly vertically and scares the bejeezus out of you. God help you if it's blowing up a storm like it was for us, I've had more pleasant boat trips across the Irish Sea in winter. Next to no information or itinerary given for when you're actually on the boat. And worst of all, the staff (ProSail, not Contiki) were so damn rude. Usually I can rough it pretty well - I loved the Outback Tour - but their constant hostile, sarcastic attitude killed what little 'ah well, it's not perfect but it can still be fun!' vibe you might have had.
The last night, you sleep on the boat just outside the marina (seriously. What is the point? Just let me off this damn boat so I can check into a hotel). Then you get back to the mainland and find everyone else on the tour has had 5 star accommodation and an awesome time and have totally bonded with each other whilst you've been stuck on a boat getting the ***** with everyone because you're sleep deprived, feeling gross and you're pretty sure someone stole your booze out the eski.
It's also so exhausting that you don't really enjoy the next couple of days until you're properly rested. Unless Contiki switch to a nicer yacht with nicer staff, save your money.