Basically my first reaction to putting on a track I was mixing was "it will burn out my ears" - basically if you've overcooked your mid-range it will tell you in no uncertain terms. Mixes that sounded clear on my near-fields sounded messy on the C5a. But it was nice to hear my carefully layered kick drums cut through.
I cant believe I have done without a full range speaker for so long! Frankly if yr mixing for the iTunes generation, this is way more useful than a nearfield. But after 15 minutes my ears had had enough exposure I had to turn back to the lush sound of the nearfields!
I listened to commercial tracks - N-Dubz Against All Odds sounded harsh and bright; Adele sounded good but her voice sounded over EQed; Katie Perry TGIF - hardly any bass whatsoever, voice cut through it is so BRIGHT! Clearly some people arent checking their mixes with a grotbox enough?

And it was Mike Senior that got me to take notice of full range speakers - thanks Mike!
Well recommended and for the price of a single speaker that is less than 2 petrol refills in a saloon.