I've used it, got a cheap 2yr signup offer a while back and it seemed like another good place to list scripts.
I like the site and how you can tailor your listing for each script so much.
You also get some view stats too which is good...
And it's a big but, I've never had anyone contact me having seen my scripts on there, so yes it's cheaper but it may not be effective.
I have had contacts for shorts and feature reads from Inktip (and here of course), never used Blacklist so wont comment... of course that's all just my experience and opinion, may be different for others.