IGN PC has reviewed Myth III and gave it a score of 8.7 out of 10. To put things in perspective, IGN gave Myth II a score of 8.9 out of 10 back in 1999.
Bugs didn't play too big of a role in the review, though some were mentioned. I was particularly disturbed by the apparent lack of veterans in the single player mission:
One sad fact that seems to have been taken away, or maybe there's a bug, is that unit experience doesn't look to carry over from level to level. I'm actually hoping this is a bug, because that feature was a big plus to my experiences in the last two games. Originally, units build experience and get quicker and more accurate every time they kill an enemy. But unfortunately I began most missions with totally fresh units even if the same type of units were used in the previous mission. Without having units carry over, the fear of losing important and experienced units goes away and so does your fear of losing them and sacrificing units becomes less of a tough decision. Sorry little archer guy, but you need to be fed to the mean old Trow now to buy some time for my demolitionists... sad little archer. I didn't even bother naming any of them this time around even though that feature is still there.
As far as the single player missions go, IGN had a hard time deciding whether it was solid or not:
The difficulty level is still right up there (and harder if you have the same unit advancement problems that I did) and you'll have to do some serious thinking and unit management with formations and placement if you want to get through some of these tough missions. I'm actually a little mixed on some this. There were some really great missions in the game that I had some trouble with and had to rethink a few times, but there were some that just... seemed a little less thought out. I'm talking particularly about some of the hero missions when you take control of Connacht, Dumas, Ravanna, and Myrdred. These missions basically required you to rush every enemy you came across with the exception of a couple of basic puzzles that need to be solved. The hero missions in the last games took more planning and thought to use the heroes wisely. I only lost one of the heroes once and that was because I was a complete dumbass. But there are also some wonderfully fun maps that challenge you to attack and defend against great numbers of creatures causing some wonderful chaos.
It doesn't sound like IGN even tried multiplayer at all, only suggesting that the new units should add to the experience.
A few points got knocked off for slow load times for saved games, which have plagued the series since TFL. This aside, IGN really enjoyed the game and feels Myth III is a worthy continuation of the series.