Using a 2.1 right now (same as the ko vfs-1 pro comp btw, if u are wondering), but WOW is the only word I have for it.
The GOOD:
Incredible adjustability for every driving style, condition you may encounter in the r/c racing world. I will argue it to be the MOST adjustable esc avaliable on the market.
Its got as much power and speed as any high end esc I have seen.
Incredibly efficent (I think i am getting more run time because of this ESC compared to my old one)
The WORTHY (to mention):
Remember to get the "Ko propo ultra shottky diode DOUBLE" if you run mod.
The 2.1 only comes with the "Ko propo ultra shottky diode SINGLE" (I think its good down to 15T)
ALWAYS RUN WITH A DIODE! don't blow up your quality ESC!
Cap is optional, but I run mine with it (infact I use 2), gives the car great punch!
Yes this thing has a thermo cutoff, but its 10 degrees higher than the vfs-1 pro version (which is the same as the hara 2.0). (Well suited to mod runners and high temp countries)
I love my 2.1, so i pamper it with a heat sink (some will use a fan too). (I only run 19T so the heat sink is good for me).
Attach your diode near the ESC side, KO recommends you keep it near the motor, but IMO, makes no difference, works very well near the ESC! (Just to make it sound convincing, I think Hara has his diode near the ESC as well)
Possible BADs:
1. expensive to program this thing, $90 cable to program on the computer or using hand held, but buy one. Programability is the best feature on this thing IMO.
2. not water proof (but I don't care)
3. doesn't bake cookies (bound to get hungry when racing for long period of times)
4. Air "worsener" in 3 seconds. (no reverse polarity protection (don't plug your battery in backwards) , so OPEN EYES are needed to operate this device)
Final Opinion:
9.5/10 for product quality. This beast of an ESC will be at least as good as the best ESCs on the market or better. Given you know how to install and use it.
6/10 for instructions and ease of use (what instructions? Lucky thing I can understand pictures) (ask the ppl on the KO VFS-1 thread if you need help). Programming ESCs is not everyone's cup of tea, if you are thoes "solder and go" people, best not use the product.
9/10 bang for buck. Superior technology (no one to my knowledge has trigger finger .9 KHZ - 12 KHZ VFD with 32x64 programable modes). However the price is steep, due to things you may need to buy such as an extra diode and programming wire. (Costed me $300 USD a few months ago)
I LOVE MY HARA TWISTER 2.1!!!!!!!