From my perspective as a not-trendy, not-woman, and most definitely not-flexible person, Let's Yoga is a neat piece of software that doesn't quite work as a "game", but is still worth checking out if you have interest in yoga. The DS as an exercise buddy is a strange concept that actually works better in practice than you'd imagine. The tilting screen helps make poses visible as the model on-screen demonstrates, and there is a nice recorded voice throughout each routine that explains each step of the pose. As you practice more frequently, you will rely on the voice over the visuals, but there is a nice mode in Let's Yoga that showcases each pose and allows you to pause the action and rotate the model 360-degrees. This is really important for people that need more time to work their way into a pose and especially for beginners that need tips and ways to simplify a pose. My gripe is that the simplified pose instructions aren't recorded in the voiceover that plays during the normal routine. Beginners need to know how to modify poses to allow for less flexibility, but the main routines don't provide any direction along these lines. The information is here, but buried too deeply. This is a misstep considering the demographic that is likely to pony up for Let's Yoga is probably not comprised of yoga veterans.
The motion capture that went into creating the pose demonstrations is excellent and you can modify several of the visual elements to fit your personal style. It occurred to me at some point while playing that the tall, skinny ladies shown in the game are only representative of the 1% of the population that won the genetic lottery and became fashion models. It would have been nice to see more "real" body types on display here...