As of now the process of populating a repeater is quite slow. Even when you have all the data available in the client side it still takes too long and it should not.
It’s a bad user experience and there’s no justification for this delay.
It’s slow even if you have a very few graphic elements (besides the item container itself).
Try to assign an array of 20 items and see it yourself.
Please try to speed it up.
Thanks,