During my time in Vegas, I visited Lemongrass a number of times. It was always very good. Consistently good and had good service as well and at a reasonable price.
I eat a LOT of thai food and I have to say that Lemongrass has some of the better Thai food I've eaten, not the best, but it's very good.
I often started with the chicken satay which is standard but good and/or the tom yum soup which had a bit more flavor than a number of other tom yum soups I've had.
For the entree, I've had a number of things. My favorite Thai dishes are yellow curry and panang curry and Lemongrass offers high quality curries, both had good flavor and spice without overwhelming and the consistency of the curry was correct as well, not too runny like some places.
They have plenty of fried rice options which are good and also offer a good pad see ew. One of the times I was there, a friend got the crab which was a full crab on a plate. I'm allergic, but it was very cool to see and looked incredibly fresh and delicious.
Overall, I always enjoyed Lemongrass and would gladly recommend it to others.