Million dollar question there Bigamp LOL
When I started I was a fanatic about doing a "full treatment" prior to ripping. After scribbling green ink over too many CDs, and trying literally every paste, powder and spray I could find, I settled in on a routine of Mapleshade's Optrix spray wiped off with Kimwipes (lab grade tissues for optics) and then a shot from their anti static zapper prior to ripping. (If nothing else this improved playback when I took a disc to play in the car)
When I broke down my system for some remodeling I put all my secret sauce stuff away and digitized new CDs right out of the jewel case. At a certain point you have to say that bitz is bitz and move on. I can't say that I have noticed a difference though I still feel a twinge of audio nervosa every time...
The distinction here is not subtle, we are not trying to keep a laser reading in real time happy; we are just trying to suck the data off the disk which is pretty standard stuff for a computer. So in my mind, laser read errors, and all the nightmare of electro-optical-mechanical playback devices is eliminated - thus the instant improvement most everyone notices.
However I am glad to have tried all the stuff. Some of the used CDs I buy have what I like to think of as peanut butter on them - then its soap and water followed by Optrix. They rip faster and with fewer or no errors.