Migration is a nice feature but I am starting to get annoyed by the bad migrated questions we are receiving. I haven't counted but my feeling is that the majority of migrated questions to cstheory are problematic. Here is a recent case:
Moderators on other SE sites don't necessarily understand what is an appropriate question on cstheory and this makes their decisions problematic. An ideal person for making the decision to migrate a question is someone who is an active high reputation user on both sites not just the sending site, but right now this is not the case.
I think that the decision about migrating a question should be made by both sides not just the sending site. We should be able to vet questions before they are migrated to cstheory, for example when a moderator on a sending site migrates a questions it should not become migrated at once but should become a possible migratable question on the receiving site visible only to moderators and high reputation users (say +2K) for a limited time (say one week) and if it receives enough migration votes on the receiving site or if a moderator on the receiving site decides that it is on-topic and suitable for the site then the migration is completed.
Another possibility is to allow high reputation users vote to unmigrate a migrated question back to the original site (with a note to the migrating moderator about it so they will be more careful in their feature migration decisions).