Ok I know, any kind of comparasion between software are usually a flameware and not really accurate.
But in my day by day work with Houdini one of my biggest bottleneck is the viewport.
It is still really slowwwww, even in the latest H10 version in Linux.
When you look at how the new softimage viewport performs, really I envy these guys:
http://download.autodesk.com/us/mnevideo/softimage_2010_new_features_video/softimage_2010_features_1300x860.html [download.autodesk.com]
Hopefully one day we also have a faster viewport like many other apps nowdays.
Just a though ….

From what others have said, XSI's (or whatever its called) viewport always was pretty speedy.

I guess it isn't wrong for Houdini to offer the same thing. Wonder what is the main focal point of the next release. (it might be speed, it might not)