If you want to experiment for a reasonable price.

Download Liveload from the SCT Site (Assuming you have SCT)
Then get a BamaChips Race Tune File emailed to you ($50).
Also VMP Tuning Peformance Tune File ($50) and I believe he has a special going of (2 for $75 if I understand his order form correctly)
if you want to try the Mileage Tune as well.

As to expectations it helped my response and power but the big improvement was killing the Nanny (Torque Management).
Its really hard to get a decent launch when the car wont go full throttle until 0.5 seconds after the clutch pedal is released.
Hard to argue with the difference I gained in ET's and Trap speeds.

 

The screws are M4 .7 10mm for those whom are interested.

Tim