This posting is older than 6 months and can contain outdated information.
The "parsing" of the remote control IR signals takes place directly in 
the IR receiver hardware. Remote Buddy then reads the "parsed" data 
and maps it to the respective actions. So, nothing should be different 
between Leopard and Tiger as no system software other than rudimentary 
USB I/O is involved in the process. I have no influence on how the 
hardware IR receiver "parses" the IR signals, either.
Apple's Remotes use a non-standard IR protocol, so that it's likely 
that the Harmony does not get the repeats right.
Best regards, 
Felix