I think there are other engines as well, Based on the quality of the backup, parental controls and cleaner, I assume they also licensed those technologies.
My only complaints about BG thus far;
1) The Cloud Storage Drive is too slow.. 35mbps connection, and it crawls like I am on a T1 or something.
2) Adblocker is awesome, powerful, but inserts annoying BG graphic into blocked ads. This needs to go, it should remove the ad and replace it with either a small text, or nothing. (ideally nothing) Thus I do not like it the way it is.
3) Updates on system boot, I cannot seem to turn off it automatically updating on system boot, and this can slow down boot. I'd rather have it update hourly but have an option to disable updates immediately upon boot. Minor annoyance, as it only slows boot by a few seconds, still.