This Serendipity location is HUGE! I have to admit that I like the smaller New York version more. You get a 50's diner feel here, whereas I expect a small dessert-cafe feel (I know, an unfortunate side effect of the movie is expectations of fans!). The plus is that we didn't have to wait for a table. And overall our server was quick.
We had the hot chocolate and snickers sundae. The hot chocolate was great, and the Snickers sundae was HUGE. Both are large enough to share. The fried Snickers was surprisingly good with a good cruchy crust and slightly warm interior.
I don't know if this place is good enough for me to tell others that you MUST go while in Vegas, but if you are a fan of the movie and have time...pay them a visit!