The thing I like best? The worldbuilding, definitely. It's an interesting challenge, trying to spin it in a completely new direction without ever coloring outside plausibly canonical lines, at all; the whole "pick one change, see what happens from there" type AU.

The thing I like least? Well, it's not precisely part of the story; but it's a tie between the necessity for canon review (I'd forgotten how much I struggled with the later books) and that particularly prejudiced, snooty kind of reviewer that's convinced I'm doing it wrong and not above lecturing me what I should do/should have done instead. Or even, in a particularly irritating variation, why exactly I lost them as a reader and am going to lose future readers as well! *sigh* Megafandoms; this is why I don't play in more of them.