E.Coli glycerol stock - (Dec/21/2010 )

Ok so I am freezing down some Top10 E.coli bacteria with my plasmid of interest in, I was planning on freezing down in glycerol but when I look online the concentrations advised by various protocals vary wildly from 10% glycerol up to 80%. I know glycerol makes the freezing process less harmul to the bacteria, but what effect does the massive differences in % make, or does it not matter too much?

It's not too important. I would suggest 15% as a target value, giving you some leeway in pipetting error. E. coli does not grow well in high percentage glycerol, but will grow at 10%, so you can grow overnights at 10% and put them directly into the -80 freezer.