I'm happy with my HP Tuners, I just started playing with it today. Took away CAGS and set my speed limiter to 200mph. I have a manual, but there are a lot of neat mods you can do for the auto - all your shift points, torque management, etc.
If you already have a laptop (at least a 300mhz with 64+MB RAM) it's the way to go IF you want to customize it and play around versus pushing a few buttons. Had to pick up a serial to USB adapter for mine, most new laptops don't come with a 9pin anymore. No big deal - $12 mail order or $30 at CircuitCity.