As a 3D Printer Marlin user for 4 years I started with this Marlin REV: 06.13.16, version 1.1.0-RC6-Bugfix.

I have flashed most Marlin 1.x.x versions stopping at Marlin 1.1.9bf for the longest duration of time.
Now running Marlin 2.x.x I have flashed all release versions and even a few bug fix version stopping on Marlin 2.0.6.3 longer than any other.

Had some crazy errors using Marlin 2.0.9.3 and reverted to Marlin 2.0.9.2 which is working very well an my latest hold version of Marlin.
Yesterday I heard about Marlin 2.1.0bf and started the configuration process though have not flashed it as of this date.
Will be doing more investigation of its newest feature MPC (Model Predictive Control) for the best performance.

All in all I find Marlin 2.x.x works very well on my Arduino Mega2560 Ramps compatible controller with the special functions that I personally use.
At some point may need more than what current controller is capable of doing, though so far benefits of upgrading far exceed previous Marlin versions.