I just hit some PLA with both a Dremel tool and a file, it seems to work just fine. Due to the low melting point, it can get too hot and glob up if you go really fast, but it wasn't really a problem.
You can also dunk it in boiling water to re-shape things a bit, and a quick pass with a torch makes the surface a bit shinier, although it's pretty shiny to start with.
Some pictures of PLA reprapped objects here:
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gallery.me.com]
Wade