Zeta 2.1 - bad latency mostly attributable to plugs?

I have just purchased Zeta 2.1 and am pleasantly surprised by its live playability (using Zeta's built-in VST host version).
 
I am using the Korg microKey USB keyboard plugged into a i7 powered laptop.
Sound is going out over a Cakewalk UA-25EX interface.
 
ASIO set at 228 samples.
 
That should result in bad latency performance, shouldn't it?
 
And yet, I am playing fast-attack sounds on Zeta 2.1 and I really have to pay attention to notice any delay at all. And I play synths with built-in sound generators, so I'd say I'm fussy.
 
Quite apart from that, I am enjoying the presets, very impressive, but it's a complex beast and I wonder if I'll ever understand it well enough to come up with my own sounds... :(