Well, I have a labelmaker at home, but haven't persuaded my employer to buy me one for work purposes (I haven't really tried very hard.)
My impression is that, like a lot of GTD, it's a matter of psychology. For many people presentation of information seems to make a huge difference to how they perceive and use it. I don't think I'm one of them, but I'm prepared to believe that for many people having nice labels on files really does affect their behaviour.
I'm quite happy labelling my work folders with a black whiteboard marker in large, clear print. It's certainly quicker than using a labelmaker, though it doesn't really allow for reuse of folders.
Having said that, I also like my labelmaker at home; not so much for labelling files, but for labelling equipment. I wouldn't really like scrawly handwriting on display, but it's nice to have printed labels on all my plugs, power adapters, in/out/etc trays, plastic storage boxes, and so on.
My advice would be: if you think it'll help get one, if you think it won't (or it isn't) then don't bother. If you can, borrow one to try first (but probably not from a labeller-obsessed GTDer

).
aef