Marlin 1.6.6, released in early October 2017, matured Universal Bed Leveling to the point that I HIGHLY recommend converting to this release. Despite its name, UBL is quite a bit more than just “level”, it is a true mesh that significantly helps Layer 0 quality.
This is especially compelling for Delta/Kossel printers. It works just fine on Cartesian, and is worth doing there as well.
For Delta/Kossel, combine Universal Bed Leveling (G29) with Auto Calibration (G33) and life gets very good.
For those who have never messed with it, “Auto Calibration”, G33, probes the bed, but it is not leveling… it is figuring your exact rod lengths, errors in tower position, and more. When it finishes (and is stored to EEPROM), your printer will be much more precise.
An example of how to use both Auto Calibration and Universal Bed Leveling on a specific printer, an Anycubic Kossel Linear (not plus) can be found here.