Yes.
A few years ago I would have said it wasn't really worth it. But times have changed and moved on.
Amex is becoming more and more popular, I have one Amex cards in my wallet and my hubby two. Most of my friends now have an Amex card in one form or another. The reason for this shift is that Amex have decided to move into the area of branded cards where they are the authoriser, rather then their own credit / charge cards. A lot of airlines now offer miles earning credit cards that use Amex (Virgin Atlantic for example which is why a lot of my friends who fly Virgin have one).
The big "problem" for retailers with Amex has always been the higher authorisation fee, but I don't see this as a problem. Historically those with Amex cards (particularly the charge cards) have been on higher incomes, and importantly with more disposable income so likely to spend more on treatments / products.
I would definately take Amex, especially if others around you don't. Those with Amex who are using it for the reward points will prefer to go somewhere that will help them get their free flights.
Some places I have known have put a "surcharge" on Amex transactions, this is very bad for two reasons. One it is a very bad PR / marketing policy and two it is a breach of the Amex terms & conditions - a surcharge must be applied equally to all cards or not at all. If you wish to have a surchange, put a 50p / £1 charge on transactions under £10 or £15.
Mat
Actually the more I think about it the more I wouldnt want to take them as there sometimes is only a small mark up on retail so even if they were buying products I would lose out 
