As for how it tastes, opinions are mixed. According to the Evening Standard, the taste is "strong, like a potent cold brew," while employees at Metro who tried it described it varyingly as "odd, but not unpleasant" and like "Water…but an aftertaste of coffee." It's also a bit of a stretch to claim that it's totally colorless, since it has a very slight yellow/brownish tint.
To try it yourself you'll need to pop on over to London, where it's currently stocked at Selfridges and Whole Foods. Otherwise, you can order it online, where 5-packs go for about $20, which is still cheaper than a pack of Crest White Strips. Expect to wait a while for your CLR CFF to arrive, though -- Internet buzz has drummed up so much interest that they're currently running on a four week delay.