check out the SIDS website, i think they list all the safe co-sleeping guidelines.
if it is something you want to do and it will benefit you and your family, then do it, dont listen to anyone else! DD went through a stage of only sleeping on me during the day, and i now go by the mantra 'do whatever works!'. she is pretty good now, but occasionally i might put her into our bed if she won't settle after an overnight feed, if she wakes up at an ungodly hour of the morning (like 5am and i am so not getting up to start the day!), or if i want an afternoon nap as she tends to sleep longer if i am next to her.