What are the advantages/disadvantages of using Jython/IronPython/Pyjamas?
But how does it scale? 

As well as anything else.  Scalability is about architecture, not language.

Anyone use these frameworks in industry?

Yes.
EDIT
Okay, rookie here so please bear with me.  What I'm trying to ask is the following:

Is it plausible for a Python-syntax fan to use one of these options while other team members "plain vanilla" version?  Is it a matter of personal preference, or would it require converting other people to using these technologies as well?
Is it possible to easily convert between, say, Jython and Java or Pyjamas and Javascript?
Also, in general, what advantages/disadvantages have people experienced from using these in the "real world"?

I think that states a little more clearly what I'm looking for. Input from anyone who uses these technologies in the industry would be very helpful.
Thanks in advance for your insights.