Bottom line up front: the Midgard Campaign Setting is an excellent piece of work. As a DM, I strongly endorse it.
Disclaimer: I love campaign settings. In addition to doing the classics like Ravenloft and Forgotten Realms, I've tried out a lot of alternative settings for my players. Back when it was new, I sent an established FRCS party from Toril to Eberron. I've also bridged Eberron with Dark Sun (decent), and set a game in the pre-history of Eberron (better). In recent years, I've climbed all over Golarion (Pathfinder RPG) over the course of four Adventure Paths. I've even dabbled in the new edition of Midnight. Lately, though, I've found that I'm quite taken with the Old Margrave, the Free City of Zobeck and the rest of Midgard.
Bluntly, even though I've been DMing games for a really long time, the Midgard Campaign Setting helps me to tell a better story. The Central European influence is rich in role-playing flavor and helps even my novice players create PCs with solid hooks on which to craft character arcs, fears, plot complications and distinctive, memorable features. The adventures that I've run in Midgard have very well received by my players. Races like the Gearforged and regional traits like those from the Margrave forest supplement export very well to other settings, but are richest in their native land.
If you're a 3.5 or 3.75 player, this PDF is definitely worth your time. If you're a DM, I submit that it's a must-have. And if you're a hardcore gamer, you'll probably buy the printed edition, too. I did.