Signup by invitation only, and having retired before it started I don't know anyone in it who I would feel comfortable asking for one.
I don't use it that much so I don't have any real opinion on how useful/good it is.
When I've peeked in on e.g. the lisp subforum, it looked to be quite good, although that was a while ago, too frustrating to contemplate engaging without being able to be part of the conversation (which, I again emphasize, is an entirely legitimate method to avoid a variety of problems).
I've posted a couple of things on there and although there seems to be a lot less traffic than HN/Reddit (at least for the posts that were to my blog) there quality of discussion seemed to be much better :-)
It also illustrates there's a huge difference in priorities and culture between Hacker News and Lobsters. Not to mention who is participating. So, I like to read and comment on both sites as they each give me something different. People also often repost HN articles on Lobsters, too, with the Lobsters comments sometimes raising points I didn't see over here or vice versa. These two are my favorite sites for technical discussion for now.
On business side, you might like the Lobsters spinoff called Barnacles. It's open invitation right now. They're like HN for bootstrappers instead of VC-funded startups. High signal to noise ratio with good stuff on marketing & case studies of interesting business. Clifford's series right now is a good reality check for people that think doing a SaaS startup will let them focus on being paid to write code. Great opening pic, too. ;)
https://medium.com/@cliffordoravec/expect-everything-to-be-u...