James Carville, not sure if it was meant to be complimentary, but said that Cruz was fearless, and the most brilliant R he's seen in a long time.

We've all heard that Harry Reid called Cruz "a schoolyard bully." Cruz came back the next day with his response to Reid:

CRUZ: I rise today in praise of Majority Leader Harry Reid. Yesterday our esteemed majority leader said the following. Quote, "My friend from Texas is like the school yard bully. He pushes everyone around and is losing, and instead of playing the game according to the rules, he not only takes the ball home with him, but he changes the rules." Today, Leader Reid continued his demonstration of civility, referring to me as the, quote, "very junior senator from Texas." As I noted yesterday, the Senate is not a school yard. Setting aside the irony of calling someone a bully and then shouting them down when they attempt to respond, today I wish simply to commend my friend from Nevada for his candor.
He does have a way with words. I can imagine that there were even a few Ds who got some pleasure from it ... after having their arms twisted by Reid over the ACA bill, and probably other times as well. I'd guess Harry doesn't like this upstart much.