Serious photographers strongly recommend buying a "real" tripod - one that doesn't flex and will hold your camera steady for eternity. See this thread for example: http://www.flickr.com/groups/d80/discuss/72157623291149070/
That said, some people (like me) just don't use tripods very often. For me, I do recognize that real tripods are vastly superior to cheap tripods but I would rather spend $200 or 300 on something else (SB-600, SB-700, software, save toward lens, etc.) before I spend it on a tripod. But I still need a tripod for family portraits and such. So, I got a cheap consumer-grade tripod. Most recently, I got the Targus TG-P60T (as part of the Targus Black Label kit - blogged here: http://betterfamilyphotos.blogspot.com/2010/12/camera-bag-and-tripod-targus-black.html ).
One of the issues with cheap tripods is that they have a hard time holding a portrait orientation. If you frame the photo in portrait orientation, the camera usually sags a bit after you let go, altering your composition. Worse still, the quick release plate usually creeps and the camera slowly tilts downward, especially with a heavy lens.
Here's a workaround that *might* mitigate the quick release plate issue: mount the camera in reverse.
For most tripods, when the camera is flipped to portrait orientation, the shutter release side is facing toward the ceiling/sky. When the camera creeps downward, it applies a counter-clockwise force on the quick release plate - which effectively loosens the plate further, making the problem worse. Fortunately, most quick release plates allow the camera to be mounted in at least 2 directions. If the camera is mounted facing "backward" (with the shutter release side toward the ground instead of away from it), then the camera may still creep down, but the more it creeps, the tighter the quick release plate will get.
Note: one issue with this tip is that the tilt handle for the panhead will face forward (unless it's reversible like that of the TG-P60T) and MAY become visible in the shot if you have a very wide lens and a long handle.