I have 4 reasonably complex r scripts that are used to manipulate csv and xml files.  These were created by another department where they work exclusively in r.  
My understanding is that while r is very fast when dealing with data, it's not really optimised for file manipulation.  Can I expect to get significant speed increases by converting these scripts to python?  Or is this something of a waste of time?
what do you mean by "file manipulation?" are you talking about moving files around, deleting, copying, etc., in which case i would use a shell, e.g., bash, etc. if you're talking about reading in the data, performing calculations, perhaps writing out a new file, etc., then you could probably use Python or R. unless maintenance is an issue, i would just leave it as R and find other fish to fry as you're not going to see enough of a speedup to justify your time and effort in porting that code.
R or Python for file manipulation