I switched out my Inner Fire glyph for the Smite glyph in my Disc-Smite spec just to check it out. I'd heard good things about it, but I always questioned whether it would have a lot of value since Holy Fire needs to be on the target to get any benefit.
But as it turns out, you would be amazed at how many people will just run around with Holy Fire sitting there undispelled, even when there is a dispeller around. Weirdness. Anyway it's great fun. I find myself more confident about holding my own versus just trying to live until someone else comes along to kill the bad guys.
Highly recommended.