In other words: It's good when you're already playing lots of blue spells.
I usually am either winning a lot when this happens, or just untapping my lands for infi mana and not having a card draw, in the latter case FoI is really good practically stating "you win". However, if I had been playing an actually good card in it's place, I might have not gotten into this situation.
M10 really made the card a lot worse, it might still be a good option, just way way worse than it used to be and now FoI actually is no longer an auto-include. You play it, you justify it.
Personally, my Soli has been 56 cards for ages..

