My wife and I have eaten at Asian Garden 10-15 times and it is the best sushi, in both of our points of view, in the Winchester (VA), Martinsburg, Charlestown area. We go for the Sunday buffet, a feast and a good deal, and one of the few buffets that will pull us away from ordering off the menu, as the food is always fresh and does not suffer from too much time in a steam table or under a heat lamp. While on our last trip the sushi seemed just a tad below its usual excellence, it is typically the freshest around the area, with crisp, distinct flavors. The sashimi is also top notch, with nice touches like a decent miso soup and a selection of crisp and steamed appetizers (we like variety n the texture of our food, and the appetizers provide that, as do some of the specialty sushi, with crisp softshell and other ingredients. On a previous trip the sushi chef talked about gong to Baltimore for fresh fish each day - nor sure if they still do that, but it looks and tastes like it.
The service is generally top notch (though a bit distracted on our last trip), so my rating here is based on several trips rather than the last of two trips in November alone. In addition to the sushi and sashimi, I recommend the Thai Iced Tea (sweeter than sweet tea, for the uninitiated, made with condensed milk and red tea).
While the outside is less than impressive, the inside is a pleasant surprise, with shoes off booths (low, surrounded by wooden benches) in addition to traditional tables, a larger space in the current location)