My normal view with 40 branches is quite fast to drag around. If I display all the branches, dragging is still doable but noticeably jerky.
I have 4 "conditional branch formats", they are currently unchecked (disabled).
The message "Downloading branch and changeset data" is displayed for 4 seconds, then "Loading filtered branches" for 2.5 seconds, then "Calculating branch explorer layout" for about 0.1 seconds. It sounds like I can only improve on this by using the date filter.