Plus I've discovered some seriously awesome sites through them that otherwise would have passed me by.
HN seems very calm/knowledgeable community so it's very good to know that I can also ask for feedback here. I asked because for the same reason I also wouldn't want to be spamming this comm. in any way.
a) you get constructive feedback. it may be tough to swallow, but it's usually not trollish at all.
b) you get to see new products and learn just by reading the threads. seriously, someone should put together a domain or something like it, listing all these type of posts.
c) unless you're launching something appealing to hackers/startups, they won't be long term users. the cool thing is, a lot of interesting people may contact you or become a connection through this.
Even if you don't want to review the site or provide feedback, you can learn a lot just from reading the comments.
I like seeing what people are working on; and it makes me want to keep focusing on the stuff I'm working on as well.
It was one of the first things that was done on HN. It provides valuable feedback for startups and also provides a bit of motivation to launch for people struggling with their own startups.