To be perfectly honest, I'd choose it in almost every support game if I could. But people will yell at you for doing so... so exhaust it is. TBH I mainly play Janna who isn't an aggressive support. Exhaust does win you engages at bot -- it's just that if your carry can bait the opponent's, then it doesn't mean too much. The utility is great and worth it at times. Especially if you're coordinated with your Jungler.
I miss CV, but nowadays it just sucks. ADC's no longer pick up Exhaust too, so the support is pretty much obligated to. --- /|\ http://i48.tinypic.com/2pzcsv7.jpg \|/ http://www.youtube.com/watch?v=vE7x0WLz7SY