It's never worth it. Sure, it might have a good first impression, but no business card should outlast the designer themselves.
It's 2010, not 1910. Every single designer (and indeed every single person) has a responsibility to protect and conserve resources, not squander them. Plastic business cards are the complete opposite of responsible design.
I feel quite strongly about this sort of thing. Coincidentally, I also left a quite negative comment on Philip Lester's (Dreamten) blog regarding his plastic cards way back in 2008. After emailing him to find out why, he told me he didn't want clients to see any negative comments about them.
Berry, please consider an alternative and sustainable method of promotion.