It looks like the main difference between a Cane Creek S3 and S8 is that the S8 uses stainless steel bearings (the price difference is around £15). According to the headset review in WMB stainless bearings are smoother (which has got to be a good thing) and corrosion resistant but I'm sure that I've read somewhere that they're also softer than standard steel bearings. I assume that 'smoother' will reduce wear but 'softer' will increase it so do they cancel each other out? Corrosion resistant is obviously good but since the bearings are packed in grease within sealed cartridges which are in themselves in a sealed headset I'm not sure it's as big a bonus as it might be. I assume that smoother bearing run more smoothly but is this actually noticable out on the bike?

So, is it worth splashing out the extra to get stainless steel bearings?

Not in my opiion! I have an S8 and after only 100 hours or so use the bearings are shot, thats despite smearing extra grease all over the bearing casings before putting them in. I have CK on my other bike which receives exactly the same level of care and attention and the bearings are still silky smooth after 5 years with absolutely no maintanence. No quesses as to what will be replacing the S8!