The Master Trials added some solid content to Breath of the Wild, and while I wouldn't consider any of it necessary for the full experience, it's definitely an improvement over the base game.

The Trial of the Sword contains three sets of challenges, each of which boots you back to the Korok Forest upon completion. These trials place you in rooms with a set objective, which is usually routing all enemies. On standard difficulty, it's really enjoyable. But Master Mode makes it unbearable at times. (More on why later) Permanently upgrading your only unbreakable weapon is a decent enough reward for taking on the Trial of the Sword, but ultimately the completion of the gauntlet is its own reward. Play this strictly if you want something new & difficult to try in BotW.

The Hero's Path is a nifty feature which anyone who's obsessed with data (probably a lot of this site's users) will love. Being able to see every path you've taken through Hyrule is SUPREMELY cool.

The Travel Medallion is a great QOL improvement, allowing you to place a single warp point whereever you are, enabling you to return to a specific location instantly. When used strategically, this can save a lot of backtracking.

The new armor and clothing items are interesting, but most DLC armor sets quickly become obsolete because they're not upgradeable like the normal clothing you find in-game or with Amiibo. The standouts from DLC pack 1 are the Korok Mask, which shakes when a hidden Korok is near, and Majora's Mask, which renders you invisible to most enemies until you attack.

Lastly, the big feature is Master Mode. This is BotW's "hard mode". I beat BotW with 120 shrines on normal difficulty on Wii U, and then waited to play again on Switch until Master Mode was released. At first, I appreciated the additional challenge. Enemies are all leveled up by one level (Red to Blue, Silver to Gold, etc.) and powerful enemies are floating in the sky on rafts supported by Octo Balloons, often accompanied by a chest. But the real kicker is that enemies regain health once you stop doing damage to them. This adds a sense of urgency to fights, which is novel for a while, but end up feels like unnecessary padding. Late in the game, fights aren't any more difficult, they just take longer to finish. Instead of adding challenge, regenrating health merely adds tedium. The worst offender here is the Trial of the Sword. There a a handful of levels in here (I'm looking at you, Floor 10) where an enemy's regenerating health combined with the limited weapons available leaves you with no choice but to cheese the game with some exploit you found online.

I 100%ed Breath of the Wild on Master Mode. I did literally everything, from Korok Seeds to Kilton Medals. And honestly, I don't think I would play it that way again. The game's standard difficulty is how it was meant to be played, and Master Mode just makes it drag.

Not sure how I feel about locking certain features (difficulty, Hero's Path, etc.) to a piece of paid DLC.

The main course, Trail Of The Sword, is challenging. Definitely reminds me of the trials from Wind Waker, and I personally don't have the patience to accomplish the tasks. Kinda hate how it's the only way to upgrade your Master Sword, but I get it.

I think the only pro to this DLC is the bulk of unlockable gear. I'm glad that these special items take effort through riddle-solving to find them (rather than just straight-up giving them to the player), but I wish there was a bit more variety than simple fetch quests.