Alex -- Interesting point about the number of neo-pros on Grinder. I get a kick out of seeing the acceptances for familiar names. BTW, thanks for the excellent editor interviews on your site. I hope you do more of them. Any tips for finding calls for submissions on Twitter?
First, I definitely agree that The Grinder has a strong SF/F bend and a significant neo-pro presence. It might be less useful to folks writing other genres or poetry, I'll admit freely.
One of the most important elements for the Grinder to truly succeed is data. The more people are using it, the more reliable and accurate its data will be. I hope that those of you who are using Duotrope will consider uploading your results to the Grinder as well, as a means of helping other writers receive more accurate data. Also, this way you will already have your database loaded there for if and when you wish to make the switch.
In terms of finding submission calls on Twitter, it's all about following the active short fiction writers and editors. The word spreads very quickly of new magazines, anthologies, Kickstarter projects, etc.
Unless you are interested in token and non-paying projects, all worthwhile new markets are very easy to find -- they'll get talked about on here, will be posted on places like Ralan, and get a lot of buzz on Twitter and Facebook.
And thanks for your kind words about the interviews I've been posting, I definitely intend to continue doing them and invite any semipro and pro editors to contact me if they're launching new publications.