MREs aren't bad. Taste varies between passable to not bad.
Cost is high but is moderated by the fact that MREs are roughly 1000 calories each. Doing heavy labor over a high duration three a day at 3000 calories is about right. It might be a bit low if your working exceptionally hard or are fighting extreme cold. Three MREs and a couple of snacks should cover it. Most people don't need that sort of calorie intake and three MREs will cause them to gain weight.
Most people can get by quite well, even doing moderately hard physical labor, on two and a snack that work out about 2500 calories. Typical sedentary Americans, who have to set aside time to work out to get exercise, can get along fine on one fully configured MRE, main dish, two side dishes and desert for dinner; a fruit bar, oatmeal and coffee for breakfast; jerky and trail mix for lunch. A freeze-dried main dish, available as a separate item, might substitute for several smaller items.
MREs store well, how long depends on temperature:
Sustained Storage Temperatures °F Estimated Shelf-life (in months):
120° - 1 month ..........10° - 5 month
100° - 18 month ........ 90° - 30 month
80°- 48 month ........... 70° - 66 month
60° - 84 month .......... 50° to 33 ° -96 month
From:
http://www.sopakco.com/sopakco/sopakco_faq.html#