We co-slept but didn't use one of those. In the begining she slept between DH and me although he never liked that arrangement for fear of rolling on her so made (you can buy them) a bed rail which was invaluable. DD could then sleep next to me. DH and I could snuggle and we could have our own blankets while she was in a sleeping bag.
DH and I are both not small and we spreadeagle when asleep so we put the cot alongside the bed with the side taken off and lay a single sheet across the top of our mattress and over the cot mattress so DD was less likely to fall through a gap, that way she was protected from me smacking her when I rolled over and was also within arms reach.
We looked at these but decided it would take up too much room in bed, also you'd have to lift LO out to feed, thus kind of missing the main advantage of co-sleeping! (if you are bf that is).
Like Ginger and Ceolas, DS originally slept in between me and DH, on top of his cot mattress which we put on top of our duvet to stop him getting squashed.
Now he's much bigger and more wriggly, we have a bed rail (BabyDan portable one from JoJoMamanBebe), LO sleeps on top of duvet in sleeping bag, and DH buggers off to sofa when DS comes in with me! If you can get a king-size bed I would recommend it, we only have a double.