solomon wrote:Is it worth paying the annual fee when there are other excellent cards out there with other financial institutions like MC and Visa?
First of all, worth is always highly subjective regardless of topic so there isn't just one answer to your question. Even if you don't know the answer to your question with some logic you can reason that many of people do find AmEx cards worthwhile or else AmEx wouldn't be in business.
Second, crunch the numbers to help you determine if it's worth it to you. You should have an idea of what your category spend is and what rewards you stand to earn. Spend varies from person to person. The Sallie Mae suggested above is better suited for certain levels of category spend. For very high levels of category spend the old Blue Cash may be a better fit.
I don't see how you've narrowed it down to "AF versus MC/Visa". There are plenty of MC's and Visas with AF's as well. Again, plenty of people do find AmEx's with (and without) AF's to be worthwhile. We can't tell you where you stand on the matter unless you can give us more details such as your spend levels in the relevant categories.
If you still can't be bothered to do the math then dig around on myFICO. There's a comparison chart posted to a number of threads that you can reference.
solomon wrote:but I already get 5% at restaurants and 2% on groceries with the Cash+.
That 5% on restaurants will not be an option starting in 2015.