I've tried using CV instead of Clarity, but to be honest the extra mana provided by Clarity is just way too handy to pass up. If your team is working properly and dropping wards, the CV doesn't really become that required - BUT the number of times I've gone OOM during a team fight and hasty-spammed a Clarity mana boost has been numerous.

The Clarity also gives you much more laning time to work with maximising your xp + gold income. But really everything in this game comes down to play style, and the Clarity/Flash works well for me :)

CDR boots stack with everything else...

Only thing that doesn't stack is multiples of the same item.

Where does it say that they will not stack? I've not read anywhere that these items won't stack their cooldown reduction.

don't stack with other cooldowns. so once you get all your boots are doing is giving you extra movement speed. I recommend finding something else.

take cv and this is great good guide