Dear S.,
I have a 15 month old son who is just now sleeping through the night. He was also great with all the transitions and would really just wake up for a pacifier which was in his crib but truth be told what he really wanted was us.
It was really hard and we had a few nights where he cried for up to an hour before falling back to sleep, but I would suggest it is time to really lay down the law and not go in his room to console him unless it is absolutley necessary. Definately do not pick him up or bring him in your bed because soon he will think it is part of his nightly routine and expect this treatment all the time. You do not want your son to still be trying to do this when he is 2,3,4 etc...
We did a few things to ensure our son might sleep better through the night. We use the Huggies nighttime diapers which are more absorbent than the regular diapers so Jack was less likely to leak through his diaper to his clothes.
We kept a strict bedtime schedule and tried to make sure his Dad or myself really ran him around the house and played a lot from 5-6:00 after dinner but before the quiet bedtime routine would begin so he was really, really really, tired. Now that daylight savings has occurred we also tend to take him for a walk where he really walks around the neighborhood after his dinner but before his bath to help tire him out. All of these things have made the difference and we are sleeping peacefully. We even wake up in the morning now before he does so we can shower in peace too!
I hope some of this might be helpful for you. I know how hard it is to not go to him but he needs to start consoling himself more and getting back to sleep on his own.
Good luck and sweet dreams to you all,
N.