Hi, I have used the Maya wrap before when my boy was around 15 months. This carrier is very convenient from birth to toddlers. Esp when they are learning to walk, they may want you to hold from time to time and this is where the wrap comes in trendy and useful. Of course the weight distribution is not as efficient as the traditional carrier on both shoulders but that is more for younger babies.
Proper use of Maya wrap should not cause neck pain. If that is the case, the strap is too near your neck. It should covers part of your shoulder and upper part of arm, then it will not hurt your neck. For the back, yes painful if you carry for too long......However, I look at it to "take off" some weight off from me versus carrying the toddler without any aid, then it will not seems to be so heavy. Sometimes I carry the weight on my sidehip, sometimes I change the weight to my abdomen, then it should make you feel better.
You can look at the website for the proper use of it. The instructions should have some picture. Cheers.