Mike,
The main thing to be concerned with when considering a 300mm f4 non-IS is the fact that Canon will no longer service that lens. If you need replacement parts, re-calibration of the focusing system, or even a simple "check & clean", you are on your own to find an independent service technician.
For this reason alone, I would only consider the newer IS version. Unless, of course, you can get the non-IS for an unbelievably low price.
"Your" and "you're" are different words with completely different meanings - please use the correct one.
"They're", "their", and "there" are different words with completely different meanings - please use the correct one.
"Fare" and "fair" are different words with completely different meanings - please use the correct one. The proper expression is "moot point", NOT "mute point".