My current client is a major telco. They have been developing high qaulity software for decades (literally). They have heavily entrenched waterfall process. They are used to doing everything to the letter of their methodology. When I first came on site two years ago I used to dispair of them ever doing anything agile.
Today, they seem to be doing agile pretty well. Its not been a universially posiitve experience and there are plenty of non-agile values and practices still floating around. On the whole though I have been impressed that rather than seeing Agile as an excuse not to write documents, they have embraced the disipline required by a leaner software process.
I have worked with clients who were much more reactive and used to being at the cuting edge. They embraced agile becuase it appeared to legitmise the lack of structure in their approach. They produced poor software when they produced up front designs and they continued to produce poor software when the developers were ‘let off their leashes’.
Upon reflection I think my current client, with its long history of rigour and application of best practice has made far better use of the agile techniques. Maybe its becuase they continue to apply disiplince. Possibly its becuase they are very aware of the dangers of a less formal approach and are always trying to mitigate any risk that not having the waterfall in place might bring.