I have to agree with Brekkie... the four blocks were a memorable device. But the problem is for a while the same colour scheme was used for ITV2, not to mention ITV News, ITV Sport etc.
The thing is, even if the blocks weren't memorable, were they any less memorable than what replaced them which has no distinctive feature whatsoever?
The comparison to the like of the Granada logo don't really apply. ITV companies of the past were able to build recognition by a combination of being implicitly associated with individual programmes (worth its weight in gold, and diluted when the association is with everything a channel makes -- I would go so far as to say that Endemol has a stronger affinity with its target audience these days than ITV does) combined in many cases by the station personalities which counted for much more than some graphic device.
Granada was "The North". Granada was Corrie. Granada was Colin Weston (at least in its patch). ITV1 is, well, the third terrestrial station. And a graphical device is supposed to make up for this?
ITV's problem is that none of it stands for anything any more. It has no real USP. It's just a mish-mash of popular but ultimately forgettable television programmes that on the whole it doesn't even make.
Where does it go from here? One thing's for sure, some snazzy graphical device isn't going to make a whole lot of difference. It needs to define itself.