Bitsetting = Set booktype of DVD+R media to DVD-ROM - improves compatibilty with standalone players. General opinion seems to be that few players understand double layer media without it!
PI/PIF scanning = Using with test programs to assess burn quality, more useful on burners that have poorer quality on many medias - if you know the burner produces usable results, and you don't chop and change media, then you can do without.
Overspeed = run media faster than rated speed.. some burners do it by default, on a range of selected media, some can be hacked to, some never. To use, it also requires that you select, even if using a hacked "nX4all" firmware, a media which returns acceptable overspeed results (and you need PI/PIF testing to verify that).
Liteon: - doubtful burn quality, but improving with newer firmware and patch tools - favours +R media, would be overspeed friendly if it were not for the weak performance above 8x - good overspeeds on high quality 2.4x and 4x media though. Can PI/PIF test, can bitset.
Pioneer: - Good burn quality, tends to favour -R media. Some hacked firmware around for overspeed. PI/PO testing only with DVD Infopro, and not yet convinced as to the accuracy.
NEC: - Capable of good results, some firmware hacking, some firmware supports bitsetting, not capable of PI/PIF testing at all under any current software.