I think most of us discussing Inner Will know it's situational, but the problem is that the trade-off and cost of dropping the mana and GCD in PvE is questionable and dropping the armor bonus from Inner Fire for the 10% movement speed in PvP is also a bit iffy, especially in a world where Rogues will have a 1 minute CD on Sprint plus a few new gap closers and the pre-existing ones.
I don't think Inner Will is a horrible spell, but as it is and considering it a situational spell, I don't see many types of situations where I could see myself saying "We wouldn't have died if I had switched to Inner Will."