Can you describe how? I have the IKEA bulbs throughout and it's difficult to imagine how they'd be any better.

Well... they're better, slightly or more noticeably, at everything: better color accuracy, dims lower, brightness is more linear, transitions are smoother... on paper they're similar, but when you actually use them, the differences become apparent quite quickly. (Disclaimer - have some GU10 Hues and some E27 Tradfris, both RGB).

At some point though it becomes "are those improvements worth the inflated price tag" and for a LOT of people, the colour accuracy is good enough etc.

Well there's a reason I have those Tradfris ;)