I had this same issue so I am glad I found this thread.  Based on what 
Suat said, I am viewing the PointCloud in RViz on the 
/camera/depth/points2 topic with Style set to Points and Color 
Transformer set to RGB8 .  While I see the point cloud fine, the refresh 
rate is quite slow--roughly 5 fps.  The camera image and point cloud 
topics are refreshing at 30Hz according to rostopic hz.  If I set the 
Style to Billboard Spheres, the frame rate plummets to about 0.5 fps 
even with the Color Transformer set to Flat Color.  (My machine's load 
meter also rises to about 3.8.)

Could this be a graphics driver issue?  I am running Ubuntu 10.04 on a 
Fujitsu T730 tablet which has an Intel Core i5 running at 2.5GHz with 
4Gb RAM and I am not running any custom graphics drivers.  My ROS 
installation is the latest C Turtle using debian packages.  I get the 
same results whether I run the Kinect or OpenNI drivers.

A related question: is it possible to get a grayscale or false-color 
depth image like the one in the NITE demo or the one shown here?

http://www.youtube.com/watch?v=jQgnuupBUI4

Thanks!
Patrick Goebel
Behavioral Sciences
Stanford University