I currently work at a pretty big website that has visitors from around the globe. My job is to help out on the SEO, and one thing we've been discussing lately is the use of international TLD's. The ones we use range between:

* (partly) translated websites like .es and .de that serve most of the content in the country's language
* non-translated (english) websites for non-english languages (due to a lack of translations) like .ro and .cz
* english websites for english speaking countries with localized TLD's (.co.nz, .co.uk)

On one hand I really have the feeling this is causing a lot of duplicate content, especially for the last two categories of TLD's. 

On the other hand though it seems a lot like country-specific TLD's tend to score a lot better in that country's Google. Would it be advisable to keep on using these domains, or should we canonicalize them all to the .com version?