Lol, I do that sometimes. Not for a whole match, but if someone us shooting projectiles non-stop, I'll get some parry practice in. I got some good down parrying with a Remy last night. I think I had always tried to down right parry before, instead of straight down.
Practice mode is great, but nothing beats a real time player who could throw anything at you at any time...
Edit: I picked up a SFIV tourney stick. Still getting used to the feel of it, but I like it. A question for those more used to it, does the joystick activate a direction with just a small nudge? My gigas seems fickle, and I'm wondering if I just need to do more subtle movements with the stick.