Maybe a little explanation of some of the previous comments would be in order.
From his profile pic you can see that Homer runs bigger and wider tyres than standard. Not 33s but getting there. So, a measure of experience there.
Naff does run 33s on the Jaffa, so his comment is personal experience
Snowman? Meh, who cares.
Nah, he's not against them anyway.
To address Dan's question, yes 33s will definitely impact both performance and fuel economy. How much depends on vehicle and driving habits but in my own case 32" muddies turned the car into a slug and worsened fuel consumption by 10-15% against 31" ATs. In the Pajero I've stayed with the standard size for both muddies and ATs and certainly I'm much happier with that.
The 33s look great, filling up the wheel arches and giving the car some lift. But offroad, by the time you deflate to improve traction you don't really gain that much. A diff lock will give you much more traction ability and won't be cop bait either.
We do already have a fairly extensive thread on 33s, so if this turns into a repeat of that I'll merge the threads.
Dan, I'm sure that someone in Melbourne will volunteer and you'll be able to discuss pros and cons at the same time.