Went to play with an ipod touch 4G at store yesterday and i noticed its already running 6.0.1. Device seems pretty smooth eventhough there are like 20 apps running in multitask. At 256 ram, it is quicker than 3GS probably due to quicker cpu and lacks of phone ability.
Anyway, i think you can try restore the device in Itune and backup all apps, no need to start as new ipod.