GameSpot has reviewed Myth III and gave it a positive 8.4 out of 10 rating. Overall, they were impressed, but the scores were affected by bugs and missing features:

Myth III's major shortcomings are its lack of new multiplayer content and a number of technical issues. Mumbo Jumbo is preparing a patch to resolve the significant outstanding issues and plans to release its map-making tools, which should allow the community to convert popular existing third-party maps and mods, like the World War II mod, and make entirely new ones. But many of the planned multiplayer features, such as new game types and the ability to play different tribes of units against each other, have been dropped entirely.

You can also read the GameSpot Reader Reviews, which has had seventeen contributions and an overall rating of 8.7 out of 10 at this point.