I used to use another backup plugin until I used the P3 plugin to diagnose the overhead of each plugin. The backup plugin was adding much more time to page load than all others put together. So I was in the "market" for a different backup.
I just ran P3 on my site with BackWPup installed and was disappointed to see the same delay. Am I concerned about nothing, or should I activate the plugin only long enough to do a backup?
Here are a few of the plugin times, and you can see BackWPup accounts for 67% of the page time load due to plugins:
P3 (Plugin Performance Profiler) - 0.0040 sec - 0.43%
All in one Favicon - 0.0050 sec - 0.54%
Are You A Human - 0.0255 sec - 2.78%
Autoptimize - 0.0055 sec - 0.59%
BackWPup - 0.6148 sec - 66.90%
Contact Form 7 - 0.0418 sec - 4.55%