Everyone is usually so cheerful about the coming spring that very few get nostalgic about the ice melting and snow going away. I like summer, but actually it is the transitions I like best — the movement from one state to another. “Liminality” is a nice catch-all-phrase, but I wonder can we really pin it down so easily. In the cultural and religious history fields, one can point towards change of seasons being the symbolic and concrete moment when we see in action the change where our lives are fundamentally just one part. In media studies it is not so typical to think along these lines, and in science and technology studies almost certainly not. But I would like to see us taking more seriously our urge to create multiple layers of reality, all on the top of each other, and ask what is so inherently enjoyable finally in these transitions, overlays, and complexities related to them.
frans goes blog 
Your talk of much in such few lines. But I would like to respond to the question.
If I attempt to answer what is enjoyable of the transitions, in my perspective is: LIFE.
There are cyclic transitions (as the seasons), there are one way transitions (as getting old, e.g. you will not have again your milk teeth in your mouth). There are unwanted and wanted transitions, as they can be fast of slow, it also exists reflective, peaceful, joyful or painful transitions. In few words there are such a big diversity and combination of them.
However, what I found in common is each time you live “intense” any of those changes, you only can sense there is life. In life, nothing is complete constant, even if we wish to, or if we want to control it, or understand it, or make it constant, etc. There is no day equal to the previous one. Each one is unique even if there is apparently a huge routine. Life keeps its rhythm in each ones melody.
Carolina
PS. BTW, the most complex questions have the most simple answers, even if it sounds paradoxical @ least that has been my experience until now.