One disadvantage with a novated lease arises if the vehicle is off the road for a lengthy period of time (e.g. repairs after an accident) - you have to nominate the number of kilometres you wish to travel in the FBT year, and if you cannot do within the nominated range, it could prove to be quite costly (e.g. extra FBT payable). One way of getting around this is if you do 26,000km a year, nominate the '15,000 to 24,999 km' bracket - if you do 25,000 km +, you'll get a refund of FBT, and if your car is off the road and you do less than 25,000 km, you won't need to dig into the 'jam jar' to come up with extra money.
We've had a novated lease for almost three years now, and will probably go for another one when the current lease ends - but hubby is in the top tax bracket, and we do a lot of km.
Cheers
LynnH