Sometimes you want to complain about something that wasn't bad, but didn't match your tastes or interests. To do this, use the phrase "It's nice and all, but..."
For example, you can say this to talk about going to the opera:
It's nice and all, but I'm not sure that I would go again. It's just really expensive.
Or you can complain about a restaurant that was highly recommended to you:
It was nice and all, but it didn't quite live up to the hype.
Adding "...and all" makes this expression sound a little more negative than just saying "It's nice, but..."
You can use this expression in spoken English, but probably not in writing.