I have Stage 2 now, but I had Stage Zero for around 15,000 miles. Its well worth it, and now that you can get an ECU reflash with it, its probably much nicer than the old UniChip I had. It will completely change your car, for the better. It still sounds stock but feels amazing. Its not so much the adding XXhp at peak, its adding so much to the powerband that you'll notice. Vishnu is good stuff, you always know the car is going work.
I would highly reccomend it, the biggest downside I've had with them is trying to get ahold of them. Shiv needs a few more employees.