The ones I've used in the past relentlessly spam you about every little thing for every issue or tell you nothing about anything. There's very little in the way of fine-grained control.

I understand some people prefer email for following up on these things, but destroying my inbox by following a busy project is not something I'll ever do. GitHub's default is to notify project owners, issues you've participated in or actively followed, or those you're mentioned in. I think that's fair.

You can also "one click unsubscribe" to them at any time, which is great.

Others I've been subjected to are things that are barely more than mailing lists. I have no idea how people deal with these.