We had some XLIFF-friendly clients who, on the whole, had been used to translating and localising their data for a long time and were productive and well-organised.

The remainder of our clients weren't; a mixture of spreadsheets, CSVs, home-baked XML/JSON/YAML were most common. We could accommodate these providing the format was documented and we had technically competent translators for that language with the correct industry-specific knowledge.

Finally, some clients insisted on sending us PDFs, marketing materials (hopefully in PSD files but sometimes in PNG or TIFF). They couldn't understand why we had to go to great lengths to find translators who could cope and why sometimes the results weren't pixel-perfect. Of course, supplying the source materials to us to pass on to translators was out of the question.

Fun times.