According to Justin (Owner of Linklicious), he believes that it doesn't matter and only added it because of demand. Up to you whether you believe him or not but I still get all my links spidered without spinning.
Yea, we've seen no link between ranking and the spintext. And if you think about it, it makes sense. All we care about is that Google knows about your link and any link text or contextual content is 2 layers away from your site.
That said, it certainly can't hurt to use custom text there.