"Let me tell you" is a meaningless phrase used to accentuate whatever is said before or after. Similarly "Tell me about it" means, essentially, "I have the same problem/feel the same way". "It was quite a ____" is another idiomatic expression, similar in meaning to "What a _____!". Another way of saying it would be "Now that's what I call a _____!" Whatever you're talking about, you're saying that it is a superb example of whatever it is.