[Bender]

Do they work?

Not for the big search engines. They usually detect them as link farming which lowers the score. Link farms may also attract more bots and fake clicks. Some of these sites also produce some of the fake clicks using their own bots and proxies/VPN's. More useful may be references from related SaaS sites that are popular in that category or popular financial sites that discuss the related SaaS sites in my opinion. i.e. if one had a buddy that is running a similar yet non-competing legit site that is popular. But don't take my word on this as I have not been involved in seo in a while not that much has changed. I think it would be better to ask around 10 AM PST on a Monday or Friday to get more eyes on the question. I guess that would be 3AM on Sunday if you are in AU.

[AussieCoder]

That's what I was concerned about. They're all charging $29-$99 to list on them and there's a risk that they harm my SEO.

Good point about timing. Sometimes I forget we live in the future here :-)