I have also come across this comment from many Fuji users but I think you need to qualify that statement. At 5R, mabe even 8R, no worries, the S5 sensor is sufficient for beautifully sharp prints (so is any 6-8MP camera).
But I have printed many 12 x 18 enlargements and -- comparing with other cameras such as the D200 and D300 (same lenses used) -- it is clear that: (i) the S5 delivers a lower resolution (less per pixel sharpness), and (ii) the famous Fuji jaggies are visible especially when you have lines that are between 0 and 45 degrees.
So, yes, if you can see jagged edges at 100% on your monitor, they WILL show up in prints of sufficient size. If you don't normally view or print big, the S5 is a wonderful piece of hardware.