I went on a ride by myself today where I spent a good amount of time between 22-27mph on some flat or slight downhill sections, and I was keeping up with the cars with no help from the motor at those speeds, only to come upon a mild hill that would cause me to gradually loose speed until I dropped below 20mph. Then the pedal assist would finally kick back in around 19.5mph.
But by that time I'd lost a lot of momentum and I would have to stand on the pedals to maintain even 15-18mph in Turbo mode. Then frustrated drivers would start to pass me. Sometimes I'd have to downshift 1-3 gears to get my cadence back up; because my Bosche motor makes more power when my cadence is higher (over 60), where lugging it at a lower cadence in top gear at 15-18mph won't result in full power pedal assist.
So, this is basically the only instance when I'd like to override the 20mph limiter, and since it's not often that I'm not riding with my wife and that I'm trying to keep up with traffic at 25mph. It's probably not worth it to me.
The first leg of this ride was 8 miles of downhill and level ground, with an 800 foot actual elevation drop over the first 3-4 miles, but there was about 300 feet of total climbing involved during that ride (5-6 climbs needing assist). I averaged 19.4 mph according to my Bosche trip computer. I met up with my wife for dinner at that point, who had ridden her bike to work today (same trip in 45 minutes). After dinner we rode back a little over 10 miles, with about 1000 feet of total climbing, and we averaged 8.1 mph. At no point riding with my wife setting the pace did we go fast enough to have the 20mph limiter kick in.
So, I might do the mod chip someday, but not during the 2 year warranty period.