As so many reviews have focused on the bugs the game has, I will try to focus my review on the gameplay itself, as the bugs will eventually be resolved through patches.
World Adventures is an attempt to take the Sims series in a new direction. It adds a puzzle element to the gameplay. Sims go abroad and whilst there can go on 'adventures' which include collecting objects, visiting places, befriending locals and perhaps most significantly exploring tombs. The tombs are a series of rooms filled with hidden doors, rock falls, traps, secret levers and treasure. The puzzles you need to solve in order to explore the tombs are generally quite simple- pushing statues onto pressure panels, 'inspecting' suspicious wall panels and so on. They may challenge younger children, but teens and adults will have no problems with even the more advanced tombs (which are longer, but not really any more difficult).
Though there seem to be a large number of tombs, they are not randomised, so once you have solved them once working through them with a different Sim family becomes a slightly dull exercise in just clicking in the right spots. This leads to limited replay value for this expansion pack, however with the possibility to download user-made tombs, this should keep the interest going.
In order to travel your Sim must pay a fairly large amount of money, and can only stay in the destination for a few days. Later trips can last longer once you have earned enough points for a higher level of visa, but this does lead to some frustration when your Sim gets sent home half way through a tomb. Many people have complained that travel is too expensive, however Sims come home with large amounts of treasure which can be sold and will easily cover the cost of the next trip. There is also a compulsory two-day wait between trips which prevents you working through the expansion pack too quickly.
Sims do not age whilst on holiday, so Sims cannot live in the holiday worlds and babies, toddlers and visibly pregnant Sims cannot travel. Sims needs still have to be met, and you can purchase dried food and a tent to use inside tombs to avoid having to go all the way back to base camp in the middle of a level. Friends and relationships can be made, and if you wish your Sim can invite a 'foreign visitor' to stay at their house for a few days.
As you would expect from an expansion pack, the game also adds in some new wants and lifetime goals, a few new skills (such as martial arts) some extra personality traits and some new objects and building equipment.
All in all, not a bad little pack which adds a decent amount of content, but nothing so exciting that I would recommend it to someone who isn't already a Sims fan.