As for free credit, I don't think they give that out. At least I haven't read anything on it.
And I had no idea they do a half off holiday promo. I've been browsing there a lot lately, and from what I can see, they may be the number one indexing site. There's a lot of content there that can't be found at other indexers(for example nzbsrus or merlins).
Although everything found there can also be found on search engines, but I like indexers more because they're easier to read, they're categorized, and I can just browse. I'll keep checking the site for a holiday promo. And if they cut the price in half, then maybe I'll subscribe.