You can improve the load time on big programs by turning off the address coloring. This is the 'Colorize' option on the 'Edit' menu. When you load a large program, you can see loading progress in the status bar. First, you see a message that says "Formatting ... " and then it should begin to plot. One thing I've noticed, and I haven't figured out why or if I can do anything about it, is that there seems to be a long pause between the formatting and the plotting. If you wait though, it should begin to plot. One other option is to turn off the 'Plot file when loaded' option on the Preferences window. Then the file only plots when you refresh it manually.