They are definitely a good modification for a long trip, The air they feed is a little cooler, and carrying less dust or sand due to the height above ground. If you use a good quality Cyclonic head, (Mantec or Darrs) and not one of those Safari Snorkel sand suckers, it will also throw out most of the particles before they can get to the air filter,(they create a vortice in the cone and most particles are expelled out of small vents in the side, due to centrifugal force) and yes they prevent an engine hydraulic if you wade some deep water - but like the guys say, you need to use a snorkel in conjunction with (both) axle, timing case and gear/transfer box breather tubes for any sort of wading. You will rarely ever need the height of the snorkel for wading, if you enter the water correctly and create a good bow wave the low area behind the wave will be where your air intake is. BUT if you stop, lose traction or hit an obstacle, you lose the bow wave the water may then be high enough to enter the intake. I've only needed the height during competition driving, (up to the windscreen) if you drive through water that deep on an overland trip you are looking for trouble. The effects on fuel comsumption and performance are negligable and you should not have to make any adjustments. As for noise, with a larger capacity turbocharged (4litres+) engine requiring a much greater air volume, you will get a bit of induction noise, but very little with a 2.4 Turbo diesel.
As for Sand Ladders being for 'show' - when your stuck up to the axles in a big patch of Feche Feche, and you have no air left in your tyres to let out, you'll then realise how vital they are. Happy Motoring, Grif.