I agree 100% with slf's answer, but wanted to add a little.
I always warn others in this industry that we shouldn't be so zealous about anything (including not being so damned zealous). Using scrum or being agile, design patterns, standards, and hell, even maintainable code don't mean anything if you're losing business or pissing of your client.
It's not the responsibility of the client to understand software development methodologies, or anything else for that matter. As long as they understand how to pay, we should deliver what is promised.
Using agile, scrum, waterfall or whatever should be a purely internal process and need not be exposed to our clients (with perhaps the except of business-to-business co-ops). To draw the obvious analogy, this is the same as data encapsultation: the most important thing is that the object works as it says it does and not necessarily how it does it. Agile provides structure within development teams and projects. Clients don't care how we manage our teams or projects, they just care about what they payed for: results.
Whether we realize it or not, we're in the service industry: start serving.
Edit: As far as the client is concerned, results are getting what they were promised and getting what they payed for. Managing client expectations is one of the most important things to do with your client, and as the third link says, "The middle of delivering a service or project deliverable is too late to begin managing a client?s expectations."
My business is in websites. We try our best to educate our clients on the process, making sure that they know ahead of time what they're getting into and what to expect. We even have a formal "client education" packet in the works. When clients are surprised by new information half way through the project or later, it sounds like an excuse.
I fully concede that there will always be the belligerent, naive, uncompromising, rude, micromanaging, and just plain bully clients. We've been burned by them before, but you have a choice. Either stick to your guns and maintain your ideologies but piss of your client, compromise and deliver a product that is below your standards but makes the client happy, or drop the client.