For me, I guess it depends on the total amount I am buying (or even my mood!).
My AMEX card offers betwen 1.5 points per $1 spent. If I am buying something that totals $50, but has a 1.6% surcharge for AMEX, it will cost me $50.80.
I have now have the choice of using my VISA card (only 1 point per $1 spent) earning me 50 points, or using my AMEX card which earn me 76 points (50.80 * 1.5). Thus for an extra 80 cents, I am getting an extra 26 points. For me, I would be going the AMEX.
Now if I am buying something that costs much more (say $1000), with a 2.5% surcharge for AMEX), the situation is this:
- VISA card - earns me 1000 points for the $1000 spend
- AMEX card - earns me 1537 points for the $1025 spend ($1025*1.5)
Thus for an extra $25, I get 537 more points. That's almost 21.5 points per $1 spent (not a bad deal at all). I think it's more a mental thing - getting your head around the fact you could have paid $1000 instead of $1025. It can be tough to justify!
In summary, I reckon the answer varies from person to person, however for me I am OK with paying a fraction more in return for plenty of points to play with in the future.