Cruz has been one of the best things Trump has going. Without Cruz, it would have been one-on-one Trump v. Kasich at the end, and that would help the establishment. Also, without Cruz, it would have been the establishment picking the delegates instead of Cruz. Trump won't pay attention to that aspect of the campaign, but having delegates who oppose Amnesty matters even if Trump thinks he has enough delegates.
Cruz's attacks on Trump will be analyzed by Hillary and the best of them will be used in the general election. Now that there is no way for Cruz to win he should stop attacking Trump, drop out and endorse Trump. Or at least shut up.