I use an Asus Xx75A (i3-3110M @ 2.4Ghz) with standard RAM and the HDD is a Hitachi Travelstar 1TB
- in other words a pretty ordinary low-endish laptop.
Auditioning individual sounds seems okay to me, there's a small loading delay (an intake of breath at most) before the sound plays. It isn't instant like my hardware drum machines (R-70, RX-15, and ancient CR-2000!) but I don't have a problem with it.
Arturia could speed it up by caching samples for whatever is in the on-screen list (perhaps as a background process) but that would only alleviate things if you were working through the list. If you were auditioning samples all over the place it'd become a liability. You'd have to filter the list to get the stuff you want in one place, then caching would work better (e.g. filtering to have only rock snares in the list).
I don't use my music laptop for anything else (except the odd online visit such as I'm doing now) so it isn't weighed down by other software, and I keep it quick by such things as regularly cleaning unused stuff from the system registry (there are programs to automate this, e.g. RegVac). Even so, there's just a tiny hesitation before something plays. Obviously if the sample is large (e.g. crash cymbal, or a vocal or synth effect as opposed to a rimshot) then it takes longer to load.
Edit: They're also layered samples, so I would guess that if they make a lot of use of velocity effects some might load more slowly than others because of the multisampling.