I am surprised still at what strong opinions co-sleeping incites. It is a practice that was just recently (in a human history context) abandoned, and we expect our children's brains to have advanced over the course of hundreds of years to overcome the instincts of tens of thousands of years that families spent sleeping together.
This is not to mention the practical benefits--ease of breastfeeding, spending time with a child who I must be away from during the day while at work, reduced incidence of SIDS as my breathing regulates his, and body temp and blood pressure, safety in case of an emergency (I can just pick him up and take him to safety rather than taking the chance of whether I can make it into his room in time), swift and appropriate responses to his communications of needs like hunger, fear, loneliness, wet nappy, hot or cold, etc...it goes on and on, yet I still get almost angry responses from some people to this very personal choice, and disbelief in the best cases because obviously this is going to ruin my marriage and make my child clingy.
A child who moves to its own bed when it is ready is far less likely to come into the family bed later, and is more likely to be independent, secure, and comfortable. My son has never had to cry himself to sleep, so he goes to sleep each night, with me by his side, with a smile on his little face. He is learning healthy, positive attitudes towards sleep, rather than viewing it as a frightening state to enter.
If any of you would like more information on co-sleeping and its benefits, check out www.naturalchild.com or www.askdrsears.com.