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Personally I wouldn't for a website that's established with any kind of a brand or history (especially established enough to have inbound links), but I think the best way may be with 301 redirects.
I followed Google's webmaster guidelines when doing this (I moved a highly ranking .com to a .co.uk, it dropped out on the index for a few scary weeks then reappeared. It's a lot of work). As the url and anchor text may have an effect on the rank however it can change the search results for better or worse.