My sister in law has a almost 2 year old and was wondering if anybody has ever used one of these backpack carriers. She is reluctant to purchase one if it going to be a pain to use. If anyone has used one before please let me know how it was for your child. Were they comfortable? How easy was it to get them in and out? Did it make it easier to get around the park better than a stroller? Thanks, I know someone out there can help.