Lords of Madness represents a return to a level of quality not seen for many expansions. I have personally seen almost the entire set, and while the paint quality is only somewhat higher than the previous Wizards miniature release, the sculpture quality is far, far better. If you use the miniatures for D&D, DDI, or just as stock figures you will be well pleased with this set.
Paint Quality:
While this set is a definite improvement over Savage Encounters you will find numerous painting mistakes, some odd color choices, and a general lack of quality. Despite this, and certainly at a distance, the miniatures look quite handsome. It is obvious that the industrial design focus being applied to the miniature lines is paying off.
Sculpture Quality:
The digital sculpting process used to create these pieces has provided a marked improvement in the quality of the end-product. While some of the (very much) older D&D miniature sets are still superior in sculpt quality, this set shines overall and is by far and away the best current set. A few oddities of the digital process crop up: very thin sections that looks so good on the computer, and yet curl up thanks to polymer alignment (i.e. when they cool down from the mold!) Overall the set is quite handsome.
Figure Choice:
Lords of Madness returns with the current focus on "providing the pieces in the numbers you are likely to use them." The result of this is fairly good. Common and Uncommon pieces represent threats and utility miniatures that you will commonly reach for while rares and very rares present the opportunity for more ground-shaking encounters. While I am less than pleased with the inclusion of Very Rares in this set (I received three of these in an eight-box pack, and two of them in the same booster!), the fact is that you aren't going to actually use the Very Rares much. I love that stock figures such as kobold slingers and orc archers are available in plenty, while more fun, but less useful figures, such as Brain in a Jar and the Dracolich are relatively easy to obtain.
Summary:
If you are in the market for D&D miniatures for whatever purchase, this set offers good sculpts for a reasonable price. While each box only contains six miniatures, many of these are quite large and at ~$15 a box, you will find that boosters are competitive with buying miniatures from singles-websites.
Not to mention discovering just what is in each booster is half the fun.