I've started taking one 15-man halb detachment with each of my 30-man halb buses, and I've found that they work great. I like that the priest's Hatred, and Hammer of Sigmar, not to mention Divine Protection cover them as well. So, Hatred and re-rolled failed wounds on 20 halberdier attacks? Yes, please. Especially when, with some wrangling, half of those come from a flank.
I guess I'll chip in the rest of my two cents here so I don't start my own new post about it. I've played seven games with the new book, and I like it, well, most of it. I've managed to beat Ogres, Dark Elves, and Lizardmen with a 4-3 record.
At first I thought the halbs were too expensive, but then I realized I can fit 90 of them into a 2k point list. With two warrior priests, two captains (one a BSB), and a lvl 4 wizard, with either a lvl 1 wizard or an engineer. With room for other goodies, like Reiksguard, or Demi-gryphs, or a Hurricanum. So far, ninety has been enough. Haven't played Skaven yet, so, we'll see.
I feel like Warrior Priests got better. The fact that you can use multiple prayers in a turn, and they cover the detachments as well is just plain great. I think I've gotten to use Hold the Line maybe twice, but I like the extra killing power Captains give me (when they aren't targeted for destruction by my opponents, that is). I like the Helblaster a lot. I'd never used one before this book, and its fun to see your opponent running away from it. Usually I team it up with an Engineer and ignore the first misfire on the artillery die. Demi-gryphs are fun, and durable as hell; just make sure you've got them some back-up, or they're a really expensive tar-pit. I haven't run any flagellants yet, but I feel like they're really expensive for the damage they might do. I've taken the Hurricanum out for a spin a couple of times and found it useful for drawing out dispel dice, so that my prayers go off. For some reason the threat of having a unit turned for a flank attack makes my opponents jittery.
Overall, my win rate is about what it was before, and I've gotten to experiment with new models, and several different lists. I like the variety that I can take to any game. Will the book be good in tournaments? I have no idea. But then, I don't play in tournaments, so I don't really care. Like I said before, with just a couple of exceptions, I like the new book.