Having been with them for perhaps two years now, I'd say my VigLink experience was better than the time I had with Skimlinks. YMMV. I work closely with an account manager who helps get the most out of the service.
Using inserted links is optional with both services; having said that, I was a non-believer until I added the link insertion for guest visitors only. It actually added between 20-30% to net revenues.
Otherwise, if members post frequent product links in a forum, you're leaving money on the table by not going with VigLink or Skimlinks to monetize those. And having used other affiliate programs in the past, VigLink has far surpassed all of them combined. (Or to put it another way, if 100 members promise to use your Amazon link, you'd be lucky to see a dozen that actually follow through on it.)