We spent an evening at the Tang Dynasty, where we had a dumpling banquet to start followed by the music and dance show.
The dumpling banquet itself was fine - I particularly enjoyed the dumplings which were shaped into animals. However, many of them really pretty bland and I have definitely tasted better. I'd recommend asking around for a better dumpling banquet, as I'm sure you could find better in Xi'an.
But the real disappointment was the show - it was extremely tacky, and the only real talent was a lady playing wind pipes and a trumpet player. Other than that, I couldn't wait for the show to be over. The theatre itself is old and grubby, and could really do with a make over.
We paid 300RMB each for the experience, which in my opinion was a total rip off. If you have any alternative plans for an evening, I would do that.