i used a full size Arms Reach until my twins were about 6 month old, and they stopped liking their swaddles. since they could not pull up to their knees when swaddled it was still safe. if i had net swaddled them i would have probably quit a month sooner.
i really liked the set up, i also had a very firm towel roll under my fitted sheet in my bed up against the arms reach, so that when i had one laying in my bed they could not roll to the edge and plop back into the cosleeper.
when they outgrew that i took the crib i bought from ikea and took one side off (it was designed to be taken off to use as a small toddler bed, but in my case i kept the mattress level up high) and secured that between the side of my bed and the wall and used that in a very similar manner as the cosleeper. i might have been able to do the crib from the start had i planned it out and bought a very firm piece of foam to bridge the small gap where it met up with my bed, but i think the way i did it was safer and the extra cost was worth that.
one nice benefit of the crib with the side removed was that i could literally lay the top half of me into it and nurse them laying down, their head pointed towards my feet and the main bed and their feet up above my head usually flopped over my upper arm. it was a bit too easy, cause i has really gotten them used to falling asleep after nursing from day one and that did get them a bit hooked on nursing to sleep. i have worked hard now to get back on track of laying down right before they drift off.
then when they started crawling at month 9 i put the side back on the crib and then also had a crib in their soon to be nursery and started splitting them up as we did a divide and concur approach to teaching them to sleep in their own room and hopefully thru most of the night. we started with the more independent one. they do usually end up with me in the early morning but at times not till 7am now, yeah!
we now just today moved the second crib away from our room to a mixed use room/ closet right next to us to work on helping the second one learn to go it alone, they turned one last week. once he gets the basics down i will join them back together in their nursery and see how that goes.
i think my girl really does sleep better in a room without us, we will see if it improves my sons nights, he is more of the snuggler.
we are putting the cosleeper back in our room for now, on the playpen lower setting and with a good pad in it, for the possibly bumpy nights ahead with him or whoever needs it is teething and various things pop up.
one thing about the cosleeper is the the "mattress" is real a joke with how hard it is, at some point i think that was keeping them restless once they got heavier and noticed it, when they got onto really good crib mattresses they overnight got better at sleeping, also since it was nearly the same thing as our bed, i think they felt a similar emotional comfort in both and that help them be ok with sleeping in their bed next to me rather than mine.