I had the "regular cruise" that comes with the e-hydro on the 20 series tractors. I think I paid about $100 to JD Parts for the upgraded "Automotive Cruise" - which is a DIY, plug and play wiring harness. Biggest feature is the "resume" button to easily get back to your previous speeds. .....but there are some other features too....like the "roll-out" after tapping the brake, load match, etc. I have pretty much set those and left 'em alone.
It may take an hour or so to install - with the biggest issue being the switch(s) install in the right "console". Pretty easy.
I found myself using the cruise allot with the planter operation. Consistent seed drop / operation of the planter. Nice. :)