My experience with BizTalk was basically a frustrating waste of time.
There are so many edge cases and weird little business logic tweaks you have to make when you are doing B2B data integration (which is probably the hardest part of any enterprise application) that you just need to roll your own solution.
How hard is it to parse data files and convert them to a different format? Not that hard. Unless you're trying to inject a bloated middleware system like Biztalk into the middle of it.
