Well that's an interesting way of looking at it! I usually climb to the window, unlock the door from the inside, climb out through the window again and open the door like described in the link (sometimes I cheat a bit by actually opening the door before climbing out, saves a bit of time with playing with the doorknob!)
Haha, it's interesting you point out that "matching pair" thingy Richard. A couple of days ago, late in the afternoon they replaced the front door of this place I'm renting. So when I went to friend of mine later that night I thought of testing the keys before slamming the door shut, and I had a little panic moment

The key fitted, but I couldn't turn him left or right... So if I slammed the door shut behind me there was no possible way to get back in my apartment...
Luckally it didn't take long before I saw I had the wrong key in the hole..... The key from my parents home looks exactly like it and it fit perfectly. So I stood there and laughed at myself for just a moment before I left