Hunters discussing Idaho's Unit 21 highlight its challenging terrain, emphasizing the need for good physical preparation due to steep and rugged areas. Many suggest that understanding the seasonal movements of game, particularly elk, is crucial for success, as animals often migrate to lower elevations during colder months. Several hunters recommend scouting trips to familiarize oneself with the unit's layout and access points, which can be sparse. Overall, the sentiment is that while the unit is demanding, it offers rewarding opportunities for those willing to put in the effort and adapt to the conditions.