Definitely agreed in general, demo sets are not a good gauge of UI response.
The only mitigating point is the demo set I tried with is quite a new set because I went to test on the 1st couple of days it was put up, so I'd assume it's not been abused by hundreds of people before. And I also checked the gallery and it's totally empty so either the sales promoters are so on to delete the gallery every night or it's really a virgin demo set. And I also cleared all the recent apps first to ensure nothing running in the background.
So the question is since you have a proper G3, have you tried a F7a side by side with your G3 to gauge on the snappiness of the UI? For all u know, your experience might be totally different from mine.