On my 750 I had flushed the system and replaced the five hoses and thermostat. I wasn't having any issues but it was simply time to do so. At that time the bike was 10 years old without any cooling system maintenance having been done. I used Engine Ice as the replacement coolant.
Once done, I noticed the temp gauge was running about a needle's-width, maybe two, lower in temp from that point on.
I don't know which made the bigger impact, the Engine Ice or the new thermostat. But there you are as to how the machine was affected.
Engine Ice won't hurt anything. You don't have to mix it as it is pre-mixed. Flushing the system is not difficult but it is time consuming. (If you're thinking about maximizing your cooling system effectiveness, I'd suggest that you go ahead and flush the system. There are plenty of how-to videos online. Also get information on YOUR engine as there may be bolts to remove that you wouldn't think about in order to get all of the water passages emptied.) You have to wait for the engine to cool after cranking it each time. I had other maintenance things to attend to so I wasn't wasting my time during the cool-down parts.
All-in-all, I'm glad I did it.
+1 on flushing the system. I know some folks flush with vinegar, but I don't recommend it. Use a cooling system flush product. These are (or should be) alkaline and are better for the aluminum in the system. Personally, I like Royal Purple's Cooling System Flush. The cooling system has a coating that peals off and can slow coolant flow, or possibly even stop up the radiator some. A bunch of that stuff came out when I flushed my system. I don't know if it cooled better after that because of that alone or if some of the improvement was because I also added Purple Ice to the coolant.
Whatever coolant you use, make sure it is the OAT type. Do not use any coolant that has silicates! Kawasaki coolant is technically OAT, but very few coolant manufactures use the same corrosion inhibitor they do. I use O'Reily's 50/50 Universal Coolant (yellow, not the orange Dex-Cool compatible). Dex-Cool formulations may be OK, but I'd rather be safe than sorry so I avoid them.
I don't know how much more effective Engine Ice or any additives are, but Engine Ice and Royal Purple's Purple Ice additive both contain some chemicals that are supposed to increase the cooling efficiency. Those chemicals are not in most coolants.
BTW, never run straight water in a street bike unless the manual says to do so. Water is too corrosive and does not have the proper lubricity for the water pump. Racing bikes use straight water or additives that do not contain glycols because glycols are not allowed at most racetracks. They are hazardous because they are too slippery. But bike racers expect to have to replace their water pumps more often because of that, too.