Got it today, so far from a quick 5 min look around it it's a lot faster/better than the old rubbish Horizon box, though I wouldn't call it extremely snappy/responsive. The remote is nicer, it has apps for things like Amazon Prime and Netflix (though no real benefit if you have a smart TV) and its definitely a lot quieter that the Horizon box, which often sounded like an airplane about to take off.
Can't compare it to a Sky Q box as I haven't used one but if you're sticking with Virgin for the broadband it's probably worth the upgrade.