i guess i should elaborate...
The timming retard eliminator tricks the ECU into think it's always in 5th gear all of the time. Well, at least when the clutch is not disengaged.
I gaurantee you'll loose bottom end power in 1-4. Remember the factory has spent a ton of R&D cash to map each gear for fuel and spark. Why would you want to loose that functionality and always run the 5th gear map for all of your gears.... think about it.
The TRE was a quick design created to eliminate the soft rev limits for top speeds. In 6th gear once you get high enough in the revs there's a point where the timming is waaay retarded to prevent the engine from reving any further. The easieast way to prevent this is to fool the ECU into thinking it's not in 6th ever. The reason why they choose 5th instead of say 1st or 2nd as the default is because your the fuel igintion map for the lower gears wont run well in higher gears. This in turn means the 5th gear map is to fat for the lower gears. It'll run yes, but not as well as the correct map would.
btw... My bike has a TRE
but mines also mapped like mad!