Is it time to switch to a sippy cup and how to try to?

the best sippy cup that makes the transition a breeze is done by nuby - it's colored transparent plastic with soft rubber tip.. so the tip is different in shape from the regular bottle's nipple but it's soft, so the baby will easily figure out what to do with it :).. i have gotten the regular sippy cups with hard plastic tips but all my baby would do is try and munch on them and then start crying because no milk was flowing out.. also, hard tips can hurt your baby's mouth.. why not make a nuby bottle as a standard one? i will never know :).. also, do not compare your baby to your friends babies - i know, it's hard not to but try and refrain from that because you have to work at your baby's pace - not at someone else's baby.. or are you telling me that the other baby is smarter than yours?.. i didn't think so :)