I have seen the Custom Data Visualizers and I attempted to create one but I found the sample to be extremely lacking (or perhaps I am thinking lightyears ahead of the plans of the VS.NEt team again)
A sample of what I wanted to do was I wanted to be able to build into vs.net such that the data visualizer for something like a hashtable. would have an extra row. And when this row was expanded it would display 2 columns. Column 1 would show all of the keys and column 2 would show each object associated with the key. A more advanced sample would allow one to expand the object used as a key or the object used as the value. (I somehow get the feeling this latter item may be nearly impossible).
Another thing I would like to do would be to add a treeview to represent certain data.
Am I aiming at something that is easily feasible in VS 2k5 - and if so what would be a good place to start reading up on how to do something like this.

Custom Data Visualizers
Dan1
maybe it can help you
Kakurady
[assembly: DebuggerVisualizer(
typeof(Bitmap),
Target = typeof(Bitmap),
Description = "birmapVisualizer")]
I think like this ;)
therock
deepakleo2003
It looks like
Target = typeof(Bitmap), Description = "Image Viewer")]
was the key information I was missing.
Scoper
u have to implement the ISerializable interface... and
a constructor in your class with info and context parametters...
and a method as GetObjectData(info,context)
I have done my visualizer for my custom classes..
u can use any control in your visualizer...
for example an image control to show the byte[]