There seemed to be a difference of opinion here about these products, so I did my own taste test. I purchased the Datrex, SOS, and Mainstay bars. Here are my personal observations and opinions:

All three are rather crumbly in nature and seemingly dry. At first, I was concerned that this dry texture would cause increased thirst, but it was not the case. Of the three products, the Mainstay bars are the only ones that are not individually wrapped. The downside is that they do not stay as fresh if you are trying to ration them. However, the upside is that they do not have the slippery coating that seems to be present on the others, presumable to help separate them after being packed so tightly. This lubrication gets on your fingers and requires some cleaning up to get rid of it -- not something I wish to do in a survival situation.

The brand most pleasing to my tastebuds was the SOS bars. It has a coconut-ish flavor, sweet enough to be pleasant, but not too sickening. I could imagine eating several bars without wishing for some insect alternatives. The next best were the Mainstay bars. These are lemony in flavor and quite sweet, more suitable for your post-MRE dessert than survival. As stated elsewhere, these are too sweet to eat consistently for a day or two. The Datrex bars, to me, were quite unusable. They were void of taste altogether. If it came down to eating those or a string of roasted scorpions, I'd probably eat the bars, but not before giving it some serious second thought. It's one thing to eat something you find disgusting because you have nothing else; it is another thing altogether to have something else and STILL find it disgusting !!

For me, the bottom line is this: I will use the SOS bars in any small, one-day emergency kit that I assemble. For longer-term kits, I will use them to supplement other foodstuffs, like MREs or dehydrated meals.

As always, YMMV.