Don't get me wrong - it's nice that there is some abstraction layer above the database. However, when it doesn't work the way you want it to, you need to find some workarounds for things that are otherwise trivial in SQL.
Alembic... meh. Just give me the SQL and I will migrate database, no problem. But looking for the yet another syntax to perform the same thing is not my idea of fun. Not to mention that all migrations I ever did were linear - I can't imagine why someone would need dependency resolution in a db migration tool. Still, it is a kind of standard, so if you are working as part of a team... shrugs
* edit: to be exact, I don't really hate hate them... I am just very frustrated with them from time to time. :)