Non-Steam games added to your Steam Library works as normal Steam Games, partially.
Here's what it does and what it does not:
Does:
Gives you the ability to use Steam Overlay in-game. So you don't need to Alt+Tab, like in MSN.
Changes your status in green color and uses "In Non-Steam Game [Game]" instead of "Online" in blue.]
It works as a Shortcut, no need for any additional information or anything, it's like running the Shortcut on your Desktop.
Does not:
Update your Playing Time.
Update your "verified" status so you can Add Friends.
Update your Steam Rating.
Unlock anything special, it's like you would use the game normally, with the Steam Overlay.
Period.
On the other hand, I used Notepad and made a custom name for it. I typed "Steam" in there, my Steam Status shown alike "In Non-Steam game: Steam".
2 people messaged me after that and went "WTF?".