In a previous life, I was trying to import content from a Movable Type blog into Hayfever. Then I wanted to write an importer from Hayfever into WordPress. And wow the MT import format is nasty. Things that have annoyed me, in no particular order:
There’s no charset considerations in the spec. I care deeply about explicit charsets nowadays. I’m sure the implementation does something with them, but what?
The DATE atom is an annoying US date, with no timezone information.
The whole serialization format is just nasty. The WordPress importer, for instance, splits records on ‘––—nAUTHOR:’, which is presumably much more reliable (in the case that there are lines of ‘-‘ in the data), but is a fairly nasty assumption that bit me quite badly for my own importer.
The PING and COMMENT atoms seem to contain nested sets of atoms, but this isn’t indicated in any sort of general way – you just have to know that PING is special.
I’m just grouchy, I guess.