Sometimes they work great -- being able to dump from MySQL into gzip sending across the wire via ssh into gunzip and into my local MySQL without ever touching a file feels nothing short of magic... although the command/incantation to do so took quite a while to finally get right.
But far too often they inexplicably fail. For example, I had an issue last year where piping curl to bunzip would just inexplicably stop after about 1GB, but it was at a different exact spot every time (between 1GB and 1.5GB). No error message, no exit, my network connection is fine, just an infinite timeout. (While curl by itself worked flawlessly every time.)
And I've got another 10 stories like this (I do a lot of data processing). Any given combination of pipe tools, there's a kind of random chance they'll actually work in the end or not. And even more frustrating, they'll often work on your local machine but not on your server, or vice-versa. And I'm just running basic commodity macOS locally and out-of-the-box Ubuntu on my servers.
I don't know why, but many times I've had to rewrite a piped command as streams in a Python script to get it to work reliably.