Actually I like CV as well, And although Flash is a great spell (Personally I'd prefer Ghost, especially with AD Champs) I think it really depends on what champion you are and role you are.
I actually use CV + Clarity on Janna. Reasons being, I rush a Eleisa's Mircale and with the 10% cooldown from the utility tree, I have 40% Cooldown for CV and Clarity. Having a 35 Second Cooldown CV can really help the team out when the enemy team is roaming, or doing Dragon/Baron or if timed right against the enemy Jungler.
Honestly, I only do this on Janna, because Janna's movement speed is so high that I can generally already Outrun/Chase enemies even without Flash, and if it's in a team fight and I get caught by CC and end up dying, well then they wasted CC on me and focused me which causes them to usually lose team fights which means I did my job anyways. I never really liked Flash on Janna honestly, although Exhaust is still good of course, so if my adc can handle their mana then I might not bring Clarity and I'll either get Heal since It'll have 40% Cooldown or maybe Exhaust/Ghost just because it's so helpful.