I use Hushed.  I like that I don't have to buy/stash a second phone.  And, I like it for messaging.  Not so much for phone calls.

 
Here are a few observations:
- When someone calls your Hushed number, it rings on your phone.  Which, if you have a SO, depending on the timing, can result in unwelcome questions.
- I don't like having to pre-pay for the phone/data packages.
- Long messages are deducted from your account as multiple messages.
- Make sure that you 'remove' the app from the device screen (e.g. I delete the app icon from the screen display.  When I want to open it, I simply perform a search on my phone)

 
Otherwise, its been very handy.

This info is so helpful!  Today, just before seeing your post, I was searching for a burner or equivalent, and actually started signing up for Hushed after researching. But stopped because Hushed wants all this credit info, and am wary about that.