seeing that i don't camp much inside buildings (nor at established "campgrounds"), i'm with Kephart on this one: i prefer a tarp.

an 8x10' ripstop nylon version, used with a sleeping bag inside a small waterproof bug-screened bivi bag, offers lots of options.

tarps allow anyone to better enjoy the outdoors, to see what's happening around them at a glance, to use the warmth of a campfire, can cook under it, can more quickly jump into action should you need to, packs lighter/smaller, adapts to other uses (like a stand-up working space, or as a privacy "fence" for a privy, or sunshade, or ground cloth...), can hold more people than just one or two folks without going to a larger product, can be used in conjunction with a bush shelter (ie: spruce bivouac, lean-to, leaf hut, brush tepee, under evergreen trees, snow cave, et al), can be set up in odd-shaped tiny areas (like in thick bush, small ledges or along a tight trail), doesn't build up moisture from breathing, easy to dry out before packing, far less expensive, doesn't require hauling poles (but can be used with makeshift poles), comes in nice low-profile colors or in camo, far less depressing stay during days of rain, can be added to other tarps to make larger shelter, allows finding that annoying rock under you without getting out of a tent, seems easier to use in uneven ground, faster to exit if it catches fire (burning nylon is a scary material to get trapped in)...

those are what immediately came to mind.

that said, it wouldn't be my first choice is some conditions, like above the treeline on a snow covered extremely windy slope.