Charming though Siem Reap might be, its Angkor Wat that everybody comes to visit. The perennial danger with all such world famous icons is that they may fail to live up to all their hype. Fortunately there's no worry with Angkor Wat, it easily matched my expectations & even exceeded them.
Its still a jungle location but its been cleared from most temples because of the damage the tree roots do. But there's still a jungle ambience with swarms with butterflys, dragonflys, the constant squawk of parrots, troops of baboons & there are even (domesticated) elephants that ferry people on the traditional routes between different temple gates.
Its too amazing to decribe effectively so I'll rely of images. Over 2 million people visit Angkor every year so a good tip is to visit towards the end of the low/rainy season (October) as the crowds are much smaller, or try to arrange a 6 am dawn arrival.