Personally I think it's a great game! There's a lot more depth to it than any of
GW's core games, but it comes with quite a large caveat - a lot of the experience you will have with the game depends upon the type of gaming group you play with. Specifically, Mordhiem has a lot more 'D&D' style elements to it that requires some kind of complicity in the experience from your opponents. If you come at with an ultra-competitive point of view then it will be to the detriment of the game - it is possible to 'max' out certain elements and make some really horrible combinations that will make some games a waste of time and a foregone conclusion. On the other hand, if you are prepared to spend some time making some good and characterful terrain, making some scenarios and a campain/narrative (there are a lot around - check out this great resource:
http://www.mordheimer.com/ ) - if on top of this you play in a good environment with some mates, I would say as an experience there are few games that come close to it!
The rules are pretty good for the most part, there are a couple of imbalances which can be fixed with a quick player fix. The most common changes are to reduce the cost of armour by 50% (or more, it is stupidly overpriced), and introducing a -1 to hit when dual-wielding which stops every person in the campaign fitting out every character with a mace/sword combo once they cotton on that's it by far the most effective combination in the standard rules.
But like I say so much of the game, like when playing D&D, comes down to the players you are playing the game with.