That doesn't make any sense - the tip was exactly about that, how you could just use Get Info and it'd do the right thing. (And obviously you wouldn't have to select a new playlist, unless you weren't in a smart playlist, in which case you'd have to select one, but you'd have to do that with your approach too.)

RE: "That doesn't make any sense"

Okay, perhaps my English is not clear enough, after all it's not my native language...
Never mind, I'll try again:

The point is, to edit the Smart Playlist criteria with cmd-I, the selected playlist needs to have *focus* in the Source list, i.e it needs to have blue background instead of gray.
To gain that focus, it may require additional steps, e.g. hitting the Tab key a couple of times, if your current focus has been the playlist itself or the search field or the overview.

Additionally, if you have opened a playlist in a new window (something I'm doing all the time: I use iTunes as the song library for my DJ work, drag&dropping songs from various iTunes Smart Playlists to the DJ-1800 application window), the only way to open the Edit Smart Playlist window would be going to the File menu, otherwise cmd-I will open the Get Info for the selected song(s) or do nothing if no song is selected.

Setting up a custom keyboard shortcut for the "File > Edit Smart Playlist" command saves *all* those additional steps.

(I hope I made myself clearer now... :)

I can't believe this passed muster...