I tried that as well now .. it didn't change the behaviour of iTunes 
though. Basically I'm doing this:

1) Select my "1 Giant Leap" playlist and double click a song. The 
button in iTunes shows me a || for pause. 
2) Select my "Faithless" playlist. iTunes immediately changes the 
pause symbol to a stop symbol.

From then on, I can do whatever I want. As long as I don't change 
back to the original "1 Giant Leap" playlist, it will keep presenting 
me the stop button. It will stop on the first press and start with 
the first track in the "Faithless" playlist on the next press. All 
Remote Buddy is doing is to execute a small AppleScript:

tell application "iTunes" to playpause

which acts exactly like a press on iTunes' play / pause button. 
Which, in turn, gives you and me the behaviour you described. I don't 
like this behaviour of iTunes either and would rather prefer to pause 
my tracks even after switching to another playlist. However, Apple 
decided to do it different and I see no way of changing this part of 
iTunes. Sorry.

Best regards, 
Felix