I'd agree with everyone who's saying that standard T140 cranks are fine, as long as they're crack tested (Magnaflux or similar), and haven't been abused. There are quite a few ways of abusing them, from punching the sludge trap plug area to death, to mushrooming the oil feed nose with hammers (depressingly common, judging by the number I've seen for sale of Ebay that have suffered this), to running with a loose rotor nut, which hammers the rotor keyway and can even hammer the sprocket splines. I wouldn't buy a crank that had been reground, only one on std and without measurable wear. But if all these potential flaws are absent, and the crack test is passed, I wouldn't hesitate to use such a crank for a normal road bike expected to cruise at a gentle 75mph. I tend to sit at between 80 and 85 on my TR7 when on the autoroutes in France, briefly over 90 for overtaking.
The only reason for my TSS crank is that I stumbled across it incredibly cheap (£125) on Ebay, being sold by someone who didn't know what it was. I paid the 'Buy It Now' asking price and took a gamble - it looked really good in the photos, though without measurements, there was a chance it was a Harris T140 crank (which are essentially TSS cranks but with the big end journals ground to standard T140 big end diameters). I was lucky, it was a TSS. Steve Campbell told me it was the best he'd seen that wasn't brand new - hardly used, in his opinion.
I needed a set of new rods in any case so, for the £40 extra for the pair (£320 as opposed to £280 for T140 Thunder rods), it made perfect sense. I had wanted to build a really fast engine anyway, so that's where the TSS crank is going. An additional advantage of the TSS cranks is supposedly a smoother engine, due to reduced crank flexure.