Night Elves are the hardest race to play. This is true for several reasons. First, they are an entirely new race, so no one has any experience with them from the previous versions of Warcraft. Second, they don't really have good melee units, and their units tend to be fragile. This means that you need to use them with care. Third, they have three (not two) spell-casters plus their leader, and they need their spells, so it is harder to coordinate their army. However, in the hands of an expert, they are as powerful as any of the other races.
Many of the Night Elf "buildings" are actually intelligent trees, not that it has any effect in the game. Producing any "Ancient" costs one Wisp, so the practical cost is 70 gold more than the list cost. Unique to the Night Elves, harvesting lumber does not use up trees; they can get an infinite amount of lumber from each tree. If you need to eliminate trees, you have to use another method besides harvesting them.
Night Elf workers do not need to transport what they collect back to a drop-off point. This gives them a higher-than-average gold income. The lumber load collected is quite small, but the rate at which it arrives seems to be the same as for the other races. However, because they don't need to actually carry anything, their overall collection rate seems to be higher than average. This is especially true once the lumberjacks have to start walking a long way. Note that this process implies that Wisps can harvest lumber ANYWHERE, and yes, that's how it works. You can drive your Wisp to the other side of the map, hug a tree, and generate lumber.