Installed the first one a couple weeks ago, makes a significant improvement in rideability. For your others customers who may be thinking about this modification, my observations.
Background info: 2011 CBR250RA Not used for city commuting, minimal multi-lane highway. Primarily two-lane country fair weather sport-pleasure riding. Bridgestone BT-003 tires, nominally stock sizes. Speedohealer installed (the speedometer was reading over 10% high from the factory with OEM gearing/tires). Top speed and maximum fuel economy are not considerations for us. No performance modifications.
1) The 1st gear "too short" issue is completely gone, makes taking off from a stop much more relaxed. Allows us to easily clear even major intersections without having to upshift or have the revs up in the harsh-jerky range. The CBR250's engine management electronics seems to compensate well for any changes in load/ignition/fuel requirements, pulls very strong from start-off through the rev/torque range.
2) The new "shift points" work well for us, requiring less up/down shifting to keep the engine in the fat part of the torque range at the most common road speeds. As expected, it is slightly more sluggish, particularly at "lower" revs in the top gears, but the better gear-spacing/response at the most common road speeds more than makes up for this.
I also replaced the OEM chain with a DID o-ring, after only 6,000 km the OEM was surprisingly stiff despite regular cleaning/lubrication. The OEM front sprocket was also more worn than I would have expected, so both of these may have contributed to increasing vibration and wasted horsepower (when you have less than 30 HP going to the rear wheel, losing an extra 3 or 4 in the chain is a major issue). The larger diameter of the new front sprocket should help the new chain last longer as well. Next chain will be a top quality new-generation x-ring type, even longer life and lower drag.
The Speedohealer is now only set to calibrate for 5% high, which would put the OEM speedometer calibration within the "normal" range seen on most cars/bikes with OEM gearing/tires. If I didn't already have the Speedohealer, I probably wouldn't install one, a potential saving for your other customers.
So the 15t sprocket experiment is a total success. In over 30 years riding, I have enjoyed many types of bike from mid-60's 2-strokes to early 80's 1100cc UJM and full-touring to current 600cc RR supersport. Having the 15t sprocket modification on the CBR250R makes an outstanding bike a even more comfortable and fun to ride.
Thanks for going the extra mile to get this product to market and making the entire transaction as easy as possible,