I've been to Walnut Grove several times for every meal (not so much since Burgatory opened across the parking lot, but that's another story). Each time I've gone, I've had a pretty decent experience, but nothing too amazing. The food is ok, but depending on who you have waiting on you, the service can be a little spotty (which I suppose is true for any restaurant).
The decor of the restaurant is tastefully done, but to be honest, I preferred the old location further down. It felt more comfortable and intimate. The one nice thing this location has to offer is very nice outdoor seating. There's nothing better than having a couple of beers and making a meal of $5 appetizers on a beautiful evening. It's just a shame there's nothing really to look at except the parking lot.
I'd say that if you're looking to go, go during happy hour for the drink and appetizer specials or for the Sunday brunch buffet. It's not worth it so go for the regular menu because I don't think the prices are in line with the quality of the food.