I am another VT-1 535 very happy owner! I have about 7,000 miles on mine over the past two years (I only drive it in the summer months).
I got it because I was losing a bit of passion for the car in stock form. It was fun to drive, but I wanted more power. The option for me was to supercharge it, or replace the car with something new. Adding the supercharger has me once again thrilled with the car! It really adds a significant amount of additional power, and it does not change the daily drivability of the car.
I went with ESS because it seemed clear they had the most users by almost a 10 to 1 ratio over the others. Also, I had never seen a single issue or complaint regarding their products. My own experience with them has also been exceptional!