Does the Share Difficulty given to each miner matter? I am running two 7970's and am adding a 3rd here in a few days (Mainly a Gaming Rig)but mining when I am not gaming.  I was wondering though does the minimum share difficulty that BTCguild sends to my miners make a difference?  Currently it is just the default of 1 but can go all the way up to 256 share difficulty. What is going to yield the best results for my hardware?

I am still quite new so any other advise is appreciated!
Increasing your submission difficulty will reduce the number of shares you submit, in turn reducing your bandwidth costs and your pool's bandwidth requirements.

The downside for you as a miner is that increasing your share submission difficulty increases your variance in earnings. If you mine at a pool with user determined share submission difficulty (such as HHTT and Itzod) then it's up to you to decide how much variance you can bear. I've covered in detail the amount by which your earnings variance increases with increasing share difficulty elsewhere, and you may want to look there for specific details.

Otherwise, at pools which automatically change submission difficulty to keep you submitting at a constant number of shares per minute, the variance should not be noticeable over an hour, and definitely not noticeable over a day.