We have just started leaving dd (16 weeks) in a room (ours) on her own at night nb: we are sleeping in the nursery as we have yet to sort out the curtains in there (lets face it dd has taken over the entire house in anycase ).
We started because we were waking her up, not the other way around, and after 4 nights, she is sleeping from 7pm to a dreamfeed at about 10.30pm then to anything from 4.30am to 5.30am when she wakes for a quick feed and then to 7.30am. Shes is breastfeed, which I think accounts for why she still wakes in the night.
We also leave her to settle herself for naps and after her nighttime feeds and have done for about 5 weeks. She sometimes mutters for up to 20 mins, but crying is getting less and less (most nights no crying at all now) and at 7pm she is going to sleep very quickly. We started doing this on the advice of our hv, as she was getting seriously overtired and screaming before we left her to settle herself. I try and avoid going into her once I've put her down, as although it makes me feel better, it seems to just keep her awake longer and make her worse.
We put her in her cot about 5 weeks ago too (didn't see the point of getting her to settle herself in her moses basket and then switching to the cot - also she was just about kicking the end out of the basket as she is very long), she took to it really well and will now wake up from naps and lay in it quite happily for 5-10 minutes chatting to her invisible friends .
I am following her lead to an extent on timing for naps etc, trying to catch her when tired and I note times down every day. It does follow a rough routine, which means I can plan when to go out to shops/meet friends etc. I also try not to stress too much, so if I am out at nap time, I try and get her to sleep in her buggy.
Sorry to ramble on, but thought insight into another routine might be useful. I also wanted to confirm what Mogwai and others have said about leaving them to settle themselves. We didn't do it for us, we did it for her. I would happily have had her up with us till all hours, but it was obvious she wanted to go to sleep and that seemed the only for us that she could.