I've always used Encumbrance in my games... I can't imagine going without it. It makes decisions about transportation & resources relevant, and gets people away from the video game inventory mentality of "loot everything"... It's even relevant for day-to-day adventuring. The standard carrying capacity rules set your maximum weight at Strength x15, which is so high that every character can wander around fully equipped & carrying enough loot to look like one of those guys smacking coconuts together in "Monty Python and the Holy Grail"... It's cartoonish at best.
Meanwhile, the Encumbrance rules reduce your movement at Strength x5, and further reduce movement/disadvantage at Strength x10... This is absolutely relevant in day-to-day adventuring, because the equipment in the standard "Explorer's Pack" weighs approx. 60 lbs... Weapons & Light Armor combined is 15-20 lbs... That means every character that has "standard" starting equipment is going to have their overland travel rate reduced if they don't have at least 16 Strength. Obviously, the players in my campaigns appreciate the value of a good horse.