The 1 1/8in Ahead-style S-3 is essentially the same as the more expensive S-8 (£55.99) albeit with steel cartridge bearings and crown race rather than stainless ones.
The race itself has a rubber seal so although it's a tight fit - a split race would be easier for those regularly swapping out forks - it helps keep out muck from the bottom bearings.The cups pressed into the frame without any problems and feature rubber seals which have proved effective at keeping water ingress out over the two months the S-3's been on my Mtb - so there shouldn't be any problems on a road bike.
The preload is a little more sensitive to set than on my Orbit XLII but once dealt with, provides very smooth steering.The finish is excellent for the price - better than Dia-Compe's Diatech CB-2 even though they're similar headsets and part of the same company.The S-3 has a good reputation as a reliable, budget headset - and although steel cartridge bearings won't last as long as stainless steel ones, it's not too expensive (£12.99) to swap them.