Agree with everyone else- you got very lucky with your first, and the fact that your second will do a five hour stretch semi-regularly at 6 weeks of age is definitely better than average - consider yourself lucky!! As for the sleeping better on an incline, a lot of new babies are like that. We used the Rock-n-Play until 3-4 months with our second, and the transition to the crib at that point was not bad at all.
My own personal aside, I find it very frustrating that society has created this expectation that babies can and should be sleeping through the night by a few weeks of age, and if they aren't, the parents are somehow doing something wrong. My firm belief after reading up on this a ton, and watching my own kids and my friends' kids, is that biology plays a huge role and there is not much that you can do in a safe and responsible manner to alter it. Starting at 3-4 months you do want to start laying a foundation for good sleep hygiene, but before that point you're really at the mercy of your baby's innate temperament combined with the needs dictated by basic newborn physiology.
DD1 10/2010
DD2 8/2013
And expecting DS1 10/2016