Yeah, pretty much everyone notices a change of perspective that occurs more or less immediately after your first session. Once someone points out to you all the things you've been missing you can't help but start to notice them all around you, wherever you go. Because they're so new they are also interesting and your mind is naturally drawn to them. You get used to looking at these new parts of the environment you didn't notice before.
Something I only properly realised this week though, is that eventually all of those new things stop being new. In time, after you've moved past the obstacles in a hundred different ways, you're so familiar with all of the pieces of your environment that none of them stand out any more. Just as an average member of the public's mind is aware of the pavement but not drawn to it, so the parkour practitioner's mind becomes aware of the whole environment but not drawn to any particular part.
Trying to be a helping hand from NorthernParkour and the British Parkour Coaching Association