Simon is at the point now where he's in a bit of a push and pull mode. On one hand, he wants to be independent and look around and do what he wants, but at the same time, he wants to be at your side. Sometimes it's both. It's equally fascinating and frustrating.
Today, he didn't want to be anywhere but with one of us. He'd whine and "penguin" up to our legs until we picked him up, and then be unhappy once you did. He's been testing boundaries a lot with stuff he isn't supposed to touch, which isn't that big of a deal unless it's something that he might get hurt with. He's figured out how to open the patio door, and I suspect the other interior doors aren't far behind.
Fortunately, there are other times where he'll quietly play with his toys and do his own thing. He spends time assembling things and working things out. He likes to go into the bedroom by himself and watch people and cars go by from the window.
I really see why people are so fanatic about development in the first few years, because the changes are very drastic and fast. I also think that you can take it too far ("Your Baby Can Read," I'm looking at you), but generally even spending time with him, and helping him explore the world, kinda does the job.
And for the record, him testing boundaries now is a piece of cake compared to when he's a teenager. I have no bigger take away from my coaching years!