I find the most useful element of INKTIP to be the newsletter. GO ahead and list your script on the site, it may or may not lead to some hits. I don't bother with the mail out desktop 'logline' catalog - I've seen it, not impressed. But the weekly newsletter is handy for knowing SPECIFICALLY if there are people looking for your type of script.
Most of the proco's on InkTip are small to mid-level, with SOME big ones 'lurking' - usually anonymously. The newsletter will list companies or agents looking for specific types of projects. "Looking for horror film set in a house by a lake" - "Looking for RomCOM for male lead in his forties" - "Looking for action script by CANADIAN writer, funding in place" - That sort of thing. The good thing about the tipsheet is, these are 'hot' leads. These are people (usually) with funding and resources - perhaps a star or specific location - in hand, and ready to exploit them. IF your script meets their needs - you'll at least get a request for a lead. This is a more focused approach - than shotgunning it out. Of course, if you've got more than one script - of more than one type - you're in a better position. And by 'type' that can mean the same genre - horror - but different budgets. Say you've got a horror script with car crashes, explosions, and gorgeous locations - AND you've got one that takes place in a limited location with six actors. You're more likely to hit a 'request' if you've got more than one script ready to go.
It's not a lot of money to spend for tips. That's my opinion.