CSV export can take a long time, and browser gives no feedback during wait.

[kfogel]

If you do a CSV export, it can take a long time (10 seconds? 15?), and there is no clue during the wait that anything is going on. One might even be tempted to press the Export button again. I first experienced this when I did a post-OrcData-import export, which involves >1000 client records, but I don't know how much the wait depends on the size of the data -- there could be some nasty constant overhead here too.