We've had it for a few years to mixed reviews. In general I think it was a good thing, but...
It's pretty annoying the first year because everyone with an account (and all new accounts) will have to link their email address (even if it's already there) AND choose 16 images (8 likes and 8 dislikes) in order for their account to work. In some ways it feels like they are going for bank level security, and that can be a time-consuming and frustrating process for some.
And I am not sure if the "Kaptcha" functionality is part of this too, or if you already have that? i.e. If you get the password wrong x number of times - then you have to start proving you are not a computer by typing in random letters and numbers from a generated image. I really dislike IC's implementation of this because you can never tell zero's from the letter "O" (or "o"), nor capitals from lower case on letters like "z" (and "o") etc..., so often times it will take 5 or more attempts just to get past the Kaptcha which pretty much means most users give up. Not sure why these image generators don't exclude letters and numbers that can be ambiguous, but they don't.
Having said that - we are now a couple of years in - and we do a get a lot less password reset requests from parents, so it was probably worth it. I seem to think there was another reason we had to change too - but can't recall what that was now...