I've always shaved my head with the Mach III -- aside from a brief flirtation with Headblade. I always stuck with the original Mach III blades, as opposed to the slightly more expensive Mach III Turbo blades. The original always seemed to do a great job, so why spend more money and fix what isn't broken?
Anyway, about two months ago I saw a good deal on eBay and got 100 Mach III Turbo blades for $95 and free shipping. I had a few regular Mach IIIs to use up first, so I just got around to using the first Turbo blade last weekend. I've been curious to see if there was any difference. As I suspected, there is not. There's an extra lubrication strip on the Turbo, but it wears out just as quickly as the lubrication strip on the regular blade. I see no significant difference. Bottom line: buy the cheaper blade and save yourself some money.