I got this to replace the stock internals this year. I've been using it for the last 6 months and I now have enough usage to provide some comments on the mod.
Overall I would highly recommend for a budget internal upgrade. The stock forks are horribly undersprung and the cartridge kit provides both new linear rate springs as well as a new damper rod and fork cap.
Installation:
The system was as bolt on as you can make it. You remove the fork cap and unscrew the fork bottom bolt and the existing system comes apart easily. Once the new cartridge is installed, Installation requires a spring compressor to get the proper oil level (120mm)
Factory oil recommendation is ohlins 5 wt. You can see some simlarities in design to the ohlins forks for the monster 1100 in the rebound needle but to a lower price point. But for around $600 for the kit, you cant expect the same level of quality to ohlins.
Performance:
The biggest difference is the rebound circuit. You can see that the cartridge, needle and fork cap replacement pays dividends here. Much better adjustability and feedback. The fork tracks much better on bumpy roads.
On compression, there is improvement but I think its limited by the stock needle in the fork bottom. I think the taper on this needle is not gradual enough and results in an on/off feeling. I was hoping this condition would change with the new cartridge installation but it did not. The cartridge does handle bumps well but I think the limiting factor for compression is its range of adjustability. Perhaps machining the needle (or replacing it completely) would help its performance.
Overall:
I am pleased with the improvement over stock. I can't rate it against other cartridge replacements since I haven't tried them but I can tell you for agressive street use, it just works. It might be a tad on the stiff side for some (but not jarring)
I have tried the Ohlins forks on the 1100S and those are better forks. But good luck getting those for less than $1500. If you want to get 90% there with 33% of the cost, this is a good value addition. Take the extra money you would have spent on the ohlins fork and use it to buy a better shock sprung to your weight! You'll have a better overall bike for it.
Pic of bike once reassembled.