It's very popular in the trendy pubs (and chains like Wetherspoons) around here just now - I think because the quirky bottle design gives it 'shelf-presence' and is very appealing to the target audience.
FWIW my missus thinks it's great (she's a Morgan Spiced fan
) and has bought a couple of bottles in the past few weeks (after we found that it had been discounted in Sainsburys to around £18). My kids think the bottle is 'well cool!'.
I strongly suspect it has much E150 added. However, like T says, caramel in this form does have a bitter aftertaste. Think saccharin, which gives an instant sweetness but a bitter aftertaste, well E150 is much the same for dark spirits (that's why many of us can't stand the stuff in whisky, plus it can masks other flavours).
Anyway, for Kraken I doubt if it matters whether it has E150 added or not as 95%+ of it will be served in a tumbler with cola or similar mixer.
EDIT - Pete, maybe that's why the kids think it's black!