I was told that don't buy the US Army MRE, cause they have less varieties or choice to choose from. That was during the desert storm decades ago. Back then there were only 4 options available. It's even worse when the first troops (the 82nd and 101st) hit the "sand" right after Saddam overran Kuwait, they had only 2 choices of MRE available cause the non-ham/pork MRE were all "donated" to the Saudis national guards since the Saudis could not set up their field kitchen fast enough.
Imagine how sick those troops really were everytime they smell "bacon" 3 rations/day for 30 days!
Also, it was rumoured in the past the GI/grunts tried to "persuade" the Brits, and the French to "exchange" their MRE during the join training exercises. The GI loved the French Version of MRE cause they have delicious French bread available.
Guess nowadays the MRE rations are better than ever before.
Regarding the taste, that depends on the individual grunts personal taste. In general, most say it's tasty and very nutrious (around 6000 calories per MRE if I remember right). Nowadays the Army is trying to create Veggie, Burritos, Pizza and Burgers MREs to boost the Gen. Y troops morale.
For heating, in the past they were issued "heaters" for the troops to "reheat" the MRE but I was told the fume from the heaters are dangerous both to the health and exposed their position to the enemy. Plus it took long time to reheat. So, many GIs would try to find their friendly logisitics bros and sis. within the unit to turn the keys on their HUMMV, HEMETT, or 5-ton trucks, kept the engine idles and inserted the "brown bags" inside the exhausted pipes. When the MRE got hot enough, the exhausted pipes would "spit" those MRE and those MREs were really really hot.
The downside for the MREs are they are very messy and generating a lot of wet trashes. That could be a headache for the clean ups, plus that can signal your presence by the enemy when you don't dispose those wet trashes properly. Another will be the MREs are heavy and each individual MRE comes with the "brown bag" and their assortments including Tabasco. That's substantial weight for the Infantry when they are issued one week of those rations on top of the usual heavy loads of ammos, "camel bag", weapons, equipments and sleeping bags.
Some Special Ops soldiers will take the "brown bags " out of all the individual MREs and stuff all the "brown bags" into one big package to free up space and weight.