An easy mistake to make when first cooking sous-vide is to under-estimate the importance of temperature. Since sous-vide lets us be so much more flexible with time it extracts a price in temperature.
The reason for this is simple. Unlike with traditional cooking where a too hot or too cold oven or grill can be compensated for by careful monitoring of the food temperature with sous-vide our meat or fish will never become hotter than the temperature of the water bath–no matter how long we leave it in.
And complicating that is how difficult it is to actively monitor the temperature of the food–even with careful application of weatherstripping it is hard to use a temperature probe on meat in a sous-vide pouch without destroying the waterproof seal.
A final issue is the long cooking times. Too low a temperature is difficult to compensate for by simply “cranking it up” (although for meals which get a final searing you can of course fudge things a little by doing a little cooking during your searing).
And if your temperature was too high your meal might well be ruined long before you notice.
All that said, the choice of temperature is often–literally–a matter of taste. Whether you like your salmon rare (maybe 108) or a little more cooked (maybe 112) is up to you. Similarly you can have your steaks range from very rare to medium rare by fiddling with the temperature on your bath.
You can even experiment by cooking short ribs, for example, at a steak temperature to make them taste more like a chop.
So take notes, learn from others and share your findings on temperature, the secret ingredient of sous-vide cooking!–David