I took advantage of the special pricing recently offered here by Southern Car Parts and purchased a Halltech Venom Intake for my C5 (2003). I had a chance to do the install yesterday and thought I'd share some of my observations for anyone else who might be doing this.

First, I had read advertisements of a "ten minute installation". While I'm no stranger to working on my own cars, this took me well over an hour to install. Removing the stock stuff took a little longer than I expected, mostly because I'm still learning the ropes of the C5. I started by loosening up all the clamps and getting anything "free" out of my way. I goofed a little removing the stock upper shroud (big black case visible from the front with the hood open), since I ended up just pulling the bolts out through the rubber grommets. No harm done, just would have been easier to remove those two Torx bolts holding it in place first.
The installation instructions from Halltech recommend heating up their air bridge to facilitate installation of the stock mass air sensor. While I didn't have to do this (it slipped right in there), I did have to heat the stock air bridge to remove the MAF. That sucker was in there tight.
I was tempted to trim down the Halltech hose coupler a bit as it didn't seem that all the new parts were going to fit in there, but after moving and manipulating various pieces for a little while I got everything in place just as it came.
The big headache for me was refitting the stock AIR equipment. The instructions tell you to remove and reuse a 90* elbow from the stock setup for use with the new system. You need to remove the rubber grommet from the elbow before attaching it to the new filter. If you don't do this, it won't stay in place. I found this out after I had clamped everything together and tried to reattach the stock air hose. The elbow fell out and found its way down inside the front bumper. Access to the front of the filter is limited at this point, so I had to go back and remove some parts to get the elbow back out and in place. I also decided to trim a few inches from the stock AIR hose before reinstalling, as it doesn't line up well as is with the Halltech filter.
My only mods at this point are a set of stock C5 Z06 mufflers/pipes and the Halltech Venom AIS. I'm hoping to get a tune on the Dynojet before the weather here forces me to put the car away, so hopefully I'll have some HP numbers to add to my post very soon.