I've used it, and it's It's fairly simple. You sign in with Reddit, choose either posts or comments, apply any subreddit filters you want, choose the delete method, and off you go. If you have a lot of posts or comments, it will take quite some time, but it will get it done.

It also lets you edit the comment to a specified value before deleting it, which is nice, since it's a soft delete. The content remains in Reddit's database and is just labelled as "deleted."

I've not used it for any other services.