I got one of the American Express Blue Cards because I thought it might work on the bicycle racks, tabacs, etc. in France. However, it doesn't use a PIN. Does that mean that I can't rent bikes in Paris/Strasbourg, etc. What about using it a tabac or Metro?

Thanks!

No more so or less so than any other merchant who takes Amex. In other words, far less coverage than mc/visa and it is not a chip and pin card.

Any kind of Amex card is less than useful in Europe, where Mastercard and Visa reign supreme. It's not a chip and pin card, so that's irrelevant. But if you generally want a cc to use in Europe, use a MC or Visa.

The chip in American credit cards, including AE, is a different technology. And you do need the European card for bicycles in Paris -- sorry.

A tabac is just a small shop that sells tobacco products and a few other things (candy, stamps, lighters, stuff like that, and some metro tickets)although some are a bit larger and add in a rather scuzzy cafe area or used to have pinball machines, but I guess those are outdated. I think you are referring to some kind of automated machine?

Most tabacs do not accept American Express.

Any American Express card will work for the Vélib bikes. It has nothing to do with the chip but the fact that Amex does not feel that there is a major fraud risk from its cardmembers for this application. Visa and Mastercard do not feel the same about their chipless cardholders.

What are you planning on buying? In europe small purchases are generally made in cash - so don;t count on anyone wanting a credit card if you are spending less than about $10. And vendors whose business transaction are very small may not take credit cards at all - you can;t buy an ice cream cone even with Visa.

Only chip and pin technology that conforms to EMV standard will work in France. Amex card with a chip does not, so you can't, quite apart from the fact that Amex is less commonly accepted than Visa or Master.
To my knowledge, no US-issued card comes with EMV standard of C&P. Canada is rolling out EMV C&P, but you can't get one from a US branch of a Canadian bank.