I've tried having my baby sleep in a separate bed in another room, and I've tried sleep training. There is a quote that helps describe my feelings about it:
"Use discernment about advice that promises a sleep-through-the-night more convenient baby, as these programs involve the risk of creating a distance between you and your baby and undermining the mutual trust between parent and child. On the surface, baby training sounds so liberating, but it's a short-term gain for a long-term loss."
This is from an article on Ask Dr. Sears about it: SLEEP-TRAINING – NOT FOR BREASTFEEDING MOTHERS