In order to improve program performance when working with big (more than 500 downloads) download queues, please set up ReGet in the following way:

Disable automatic save of queue file (Options-Program options-All properties-General settings- Automatically save the queue-file).
Decrease the number of lines in the download log in order to decrease memory usage (Options-Program options-All properties-Log settings-Number of lines in download log).
Disable option 'Show traffic for selected downloads' (Options-Program options-All properties- View settings-Show Traffic for selected downloads).
Also it may be useful to disable option 'Animate ReGet's system tray icon, because process of animation takes significant amount of processor time, especially on slow machines.

Setup tips and tricks:

In a multi-user environment (when a few people are using the same computer) it is possible to have different queue-files for different users. Just make sure every user saves his/her queue-file under different file name, user using 'File-Save as' menu option.