As you say, it can make a big difference, especially to the wallet.
I flew to Ireland and back at the weekend in an aircraft that made it easy, with all sorts of whizzy computerised displays of fuel flow, egt for each cylinder, and a 'lean assist' function that walks you through the whole process as you do it.
The fuel flow dropped from 12 gph at full rich to just under 9 at best economy flying at around 7,000', which was more than enough to finance a few pints of Guinness.