Fast plotting?

[Russell E. Owen]

Can anyone recommend a fast cross-platform plotting package for 2-D 
plots?

Our situation:
We are driving an instrument that outputs data at 20Hz. Control is via 
an existing Tkinter application (which is being extended for this new 
instrument) that runs on unix, mac and windows. We wish to update 5-10 
summary plots at approximately 2 Hz and will be offering controls to 
control the instrument and the plots, preferably (but not necessarily) 
mixed in with the plots.

Ideally the package would create plots in the Tkinter application. But 
we realize we're unlikely to get the speed we need that way. So we are 
willing to have the Tkinter app send data to the plotting package  (e.g. 
via a socket) and have it display the plots in a separate process.

We started out with matplotlib, which is a wonderful package (and well 
integrated with most or all GUI toolkits). Unfortunately it is just too 
slow -- at least when driving plots integrated with the Tkinter app. (It  
is getting faster and so are computers, so at some point this will be a 
great way to go. But for now...)

Any suggestions?

-- Russell