I actually used to enjoy Warriors. Back when I was in middle school and was reading Redwall and Watership Down and such, it was my favourite. Now, I've found that I like the series less mainly because of Fridge Logic and disbelief.
First off, The cats act nothing like cats. Cats are not noble. Cats do not adhere to any code or law other than "stay alive and try to reproduce". Real life feral colonies are not structured like the clans. The idea of monogamous cats is especially hilarious. And kitty doctors? When most plants would wreak havoc on a feline's insides? The religion doesn't bother me too much. If cats were social animals, they might have some sort of belief system. What really bothers me is the heavy-handed use of morality. When Firestar claims higher moral ground over scourge because Star Clan is on his side. When other cats move into the mountain tribe's territory and are OMG evil because they have no warrior code. I might have been able to pass this off as the cats simply being overzealous with their religion and morals (an actual flaw), but then the Erins try to paint the Clanners as accepting and tolerant...
My second big problem was the Stus. Firestar reminds me of the Mighty Whitey archetype, in that he enters a closed tribal society, surpasses everyone else, and becomes one of the most pivotal members of said society. Brambleclaw is a little bit more rounded, but not by much. It seems that most of the cats lack distinctive personalities. The toms are all either stu-type, belligerent opposer type, or reliable warrior type. The she-cats are either "gentle" or "feisty".
To its credit, Warriors is actually rather addicting, if you can get past all the You Fail Biology Forever and Wall Bangers. Its like those Telenovellas my family likes to watch...or Twilight. Not necessarily deep or complex but a decent read. It is actually suitable for older children and preteens, and not nearly as violent and edgy as the fans like to claim. I'm not good at critiqueing prose itself, but I can say that it was understandable and that I did not find any odd word usage. Some of the secondary characters are actually quite interesting, my favorites being Graystripe, Blackstar, and Leopardstar. The Clan structure also creates a convenitent formula for fanfiction and RPG set ups.
And hey, kitty wars.