It boasts nice controls and original Yu-Gi-Oh gameplay but there are a few problems.
Nightmare Troubadour was Konami's first Yu-Gi-Oh title on DS and it seems they underestimated the graphical capabilities of the hardware. The textures are normally muddy or grainy - the summoned monsters often look like a strange mush of colours and cards and other interactive items, for example, the chest used to save the game and the figurines around it, all look very repugnantly pixelated. Some of the graphics, for example, the buttons, duellists and pictures on the mini-map all look fine but there are issues with some of the more commonly seen textures which could definitely be improved.
The card-game mechanics remain unchanged. Players have a deck of cards consisting of various different types of monster cards, spell cards and trap cards and they draw a card every turn. They can attack using monsters or use their special effects, they can get quick bonuses with a spell card or trick the enemy using a trap. To anyone who is familiar with Yu-Gi-Oh the game's core gameplay elements are only slightly tweaked and you should get to grips with the game quickly. For those who don't know about Yu-Gi-Oh, the game offers tutorials which will tell you about the basics of Yu-Gi-Oh and various strategies you can use effectively in practical situations. These tutorial are thorough and contain very helpful advise, so the game does support experienced players but also tends to the needs of people who are unfamiliar with the game.
The main method of duelling in the game uses a system where duellists are dotted around the map. This a lot of fun and the most addicting part. It runs on an in-game time, where different players can be found at different times. To find random players you simply drag a little circle called the "duellist radar", quite fittingly, around a sizeable map until you find a duellist. This is a nice interface and really adds some interactivity into finding a foe. As you win more games against these AI characters you level up. With each level up the duellists get increasingly more difficult to defeat.
The game also offers, besides finding duellists, a "puzzle mode" as it were. In these scenarios you're provided a pre-generated set of cards and you're given the winning conditions. You've then got to use your head to reveal the clever strategies you can use in practical situations, provided you have the cards.
So to my last point, and probably what makes this game so strong in comparison to its GBA counterparts, the controls. The game relies heavily on the touch-screen which is always a good reason to praise a game. All cards are summoned by tapping on the card and setting cards down is all about touching the cards too. This all adds a realistic feel to the game. All attacks are controlled by the touch screen to and you tap the monsters you want to kill or designate the monster you want to give an attack boost. The controls are all very nice and if touch-screeen isn't your thing, it pretty much supports all the DS buttons too, so the controls are great on this game.
Just like what GameSpot said, it's the controls that really win this product marks as a video game, but it's the same old great, addicting and fun Yu-Gi-Oh gameplay that really makes this game worth the buy.