I ended up liking Tithe for the most part. I liked it kind of despite myself. I didn't want to like it -- there's a very definite Francesca Lia Block-ish vibe going on. Yick. But I ended up getting pulled in.
Great politics between the Seelie and Unseelie Courts, a lot of action, a decent romance, an interesting family dynamic, lots of plot twists & turns, and one of the funnier coming-out stories I've ever heard. I'm not going to ruin it for anyone, but be aware that it involves Star Trek.
So. Who will like it? Very definitely FLB fans. Fans of urban fantasy stories. I think that anti-fans of FLB will be pretty evenly divided about it. For me, all of the aspects that I enjoyed outweighed the Blockishness.