1,(during a holiday)I say"It has been a really good holliday".

这个句子没错，表示截止说话时刻假期过得不错，说话之后假期是否会被搅黄或者还会继续很好不得而知，也不关心。如果改为一般现在时，It is a really good holiday. 则说话人认为整个假期都是不错的，虽然假期还没有结束。

2,The weather has been cold recently. 表示说话之前的一段过去时间里，天气一直比较冷。句子表示最近的状态。

3,The road is closed.There has been an accident.

4,Have you ever been on a horse before?

5,Things are expensive now.There has been a big rise in the cost of living.

以上三个句子中的be都是动态用法，表示一个事件在不确切的过去时间发生。