Unless you are targeting a specific geographical location, you should not be too concerned with the extension. TLD's are all treated equally by search engines. It�s just that .coms are easier to remember and it�s a general tendency among surfers to end a domain in .com...
�At least you have an ability within Google Webmaster Tools to say that ok, for my .co, this is actually about this country or that country...Even though it�s a country specific domain, you may do geo-targeting�
This is what Matt Cutts has to say on whether .co is treated as a generic TLD or not...
http://www.youtube.com/watch?v=k0sCn...eature=related