I'm giving the first book a try right now.
Pros:
* Lots of intrigue.
* Setting is richer than your bog standard fantasy world.
* Very imaginative set pieces.
* Gritty and evocative.
Cons:
* Deals almost entirely with military situations, and the military situations are strangely anachronistic. I don't understand how you have front lines and grinding battles of attrition involving 10s of thousands of troops over many months with pre-gundpowder armies. Nor do I understand how they conscript such massive armies, or even what the point of the Malazan Empire is. It reads like WWI with swords and wizards, which doesn't do much for me.
* Characterizations are weak. Everyone is world-weary and sardonic. Halfway through the book and lines like '"You shouldn't be so sure, Captain," he scowled,' are already becoming tiresome.
I'll try to push through it, but it'll be a struggle to finish. The author has an impressive imagination and he's not an entirely shitty writer (though he doesn't hold a candle to the Vances, LeGuins, and Moorcocks mentioned above), but he tries too hard to make it all so grim 'n tough. I just find the mix of high magic, horrific warfare, and modern military attitudes hard to reconcile.
But I may not be the best person to ask. I haven't found a fantasy novel written in the last 20 years that didn't make me cringe. And the first Malazan book is better than most of the others that I put down.