The browser type doesn't seem to change anything.
I have 3 web parts set up the exact same way on two different sites, connected to the exact same list template. One site has 1200 list items the other has 25 right now. The site with 25 items loads in 5-10 sconds. The site with 1200 items loads in 25-35 seconds.
3 web parts:
1. qlist view, in list searcher mode. About 8 fields selected.
2 and 3 qchart view web parts, 2 of them, displaying data in qlist web part. One a pie chart other a bar chart. e fields-8 total.
Page is the same, site collection is the same. Data is the same, but one loads properly the other takes forever.