After attending a few track events and sliding around in my seat I decided it was time for a harness.  A good 6 point harness was just what I needed.  Not only did it add to the safety factor of the car, but also affected the way I could control the car.  I was no longer having to brace myself in the seat or against the console in hard corners.  I can now tell when my car is sliding instead of my butt against the seat.  I don't have to think about sliding in my seat now and can focus more on the task at hand.  Another added benefit is the safety you get should you be involved in an accident/rollover/etc.  It was definitely a very worthwhile upgrade if you plan on going to the track.  They are not too expensive, around $200, for the Sparco/Sabelt belts.  

Installation

     The install is fairly easy for the most part, with just a few tricky parts.  The first thing you want to do is remove the seat.  These directions pertain to power seats, so manual might be different.  Roll the seat all the way back.  There will be 2 plastic covers over the seat rails below the seat; push down on them and forward to remove them.  There are 2, 6mm allen bolts you must remove. On the back of the seat rails there are 2 plastic covers you have to remove.  The left side just has a screw on the side you undo.  The right side has a cover on top of the screw you must remove.  Once both screws are out, you can disconnect the electrical connector underneath the seat and remove the seat by pushing it back and out.  Remove the back seat by just pulling up on it near the front of the seat.
     Next thing to do is install the shoulder belts.  Undo the rear seat belt anchor bolts and bolt the harness on top of seat belt anchors paying attention so that the dimples line up again.  Next install the left seat belt.  Remove the trim along the door jam by pulling upwards.  Remove the panel in the foot well (2 screws) and 1 screw in the door trim under the backseat.  Bolt the left belt in where the seat belt is anchored.  The right lap belt is the most difficult.  You have to undo the seat belt anchor on the seat.  Use a 6 point 17mm socket and hold the rail guide in place while you crack it loose.  The seat rail guide will have a slotted  hole for the seat belt anchor.  Look at the shape once you remove the seat belt latch.  You are going to have to modify the harness hardware by grinding a similar shape in it to get it to fit.  Bolt the stock seat belt latch on top of the harness hardware.  You are now ready to reassemble the car.  Make sure all the 17mm bolts get torque to 37 ft/lbs.  Reinstall the seats in the reverse of how you removed them.  When it comes time to bolt the front seat to the chassis, bolt the anti-submarine belt  between the seat rails and the chassis. It may take you a few attempts of getting the belt length right before you assemble it together for good.

     Final Notes

     Track days now are more fun.  I can really now feel what is happening with the car, and not have to worry about which way my body is being tossed around.  For the price, it is a worthwhile upgrade for any one who gets aggressive on the track and is looking for a new level of safety and control.  The belts also stow away nicely under the seats.  The shoulder belts I can just toss behind the back seat or stow them underneath the seat if I want, for all other non-track days.