I know everyone has there own opinion on this topic and I am wondering where you fall.
I partially co-slept with Gabby when she was an infant. I had a small one bedroom apartment and the crib wasn't that far away, but seriously, being beyond tired those dozen or less steps to her and back for the midnight (hahahahaha later) feedings was hell. I perfected sleeping in one position without moving out of paranoia for her. We never had any squishing or falling issues. She always started the night in the crib, and once she started sleeping through the night that is where she stayed.
Now I am not claiming perfection, some times I would grab her and have her sleep in the bed with us to comfort me. I mean seriously the are only that little for so long and there is just a great peace being near your child when they are asleep.
We have gone through the normal problems parents have getting their child to sleep in their own room in their own bed. I will willingly admit that when Gabby was two and three I spend more than a couple nights sleeping at least partially in her room for her comfort and security.
And like most children she started to perfect her timing and the weak parent. Meaning she would wait until Alex and I were in that deep deep sleep where you will agree to anything if the person bothering you will just be quite and go away, or in this case just get in the freaking bed already and go back to sleep.
Gabby is 5 and sleeps in her own bed 99.95% of the time. Now I some times get the cold little hand and the small little "Mommy? I had a bad dream." And some times I tell her to climb in, some times I pull my self up hug her and take her back to bed, and some times I'm evil and pretend to keep sleeping so she will have to take it up with Alex. Who by the way lets her sleep with us more than I will.
And Gabby who when we are awake can't seem to get enought Mommy and hugs and kisses, who used to cuddle so close when we would co-nap or sleep, the child who used to insist that she be allowed to lay down on my tummy like a baby and fall asleep listening to my heart. Now we can't seem to get far enough apart. Seriously. When we nap (so rare for the kid to agree to a nap) I end up all the way on one side of my bed and she is all the way on the other (granted we do spend 15 min or so talking and cudling first, but when it comes to sleeping...) Or on the rare nights she ends up in bed she is almost one with Alex ( I think it is because she gets so cold and refuses to sleep under the blankets) but still.
Long story short I personaly see nothing very wrong with it so long as you are careful and take precautions. I plan with the next one that either the crib or a basanett will be in my room flush with my side of the bed, partly because I don't think it fair for Gabby to be woken up many times a night due to the baby and partly because I remember how tired I will be. But mostly just for my own peace of mind. Once the baby is sleeping through the night s/he will make the move down the hall and Gabby will have to learn how to share her room.
Also is it 20 weeks yet the suspense and the lack of ability to plan is killing me!