staff buy-in tips?

What is it you're looking to use Casper for on these machines? Depending on what you plan to use it for perhaps you may get better advice. Is it strictly inventory? Is it to deploy software? Is to make use of profiles? Are you going to take away admin access? Manage printers? Make use of VPP?

Initially, it's just to get a good inventory of deployed hardware and software, make sure drives are encrypted, and make sure security updates are installed. We have no plans to take away local admin access. We're mostly cloud-based and do very little printing, and employees can work from home several days per week. Eventually, we may deliver software, but that's after everyone is enrolled and running smoothy and we see the need.
Thanks for asking for clarification.

@bpavlov framed up the conversation direction perfectly to start. The community needs more information to provide you the advice you're looking for. Honesty is typically a good policy, too.

What will be in it for them is what they'll (the end users) want to know.

Of course you replied while I was typing...

If that's all you're doing and you're not talking about removing admin rights for the end user, I don't think you'll encounter problems. Getting rid of admin is a big deal, and you're not doing that. Just state what you're doing as you listed, why it's important to be done, who asked for it to be done, and how you plan to resolve things when you find issues with a person's computer.

You'll know your users better than anyone on here.

+1 on @ernstcs

From personal experience with folks in a large research environment that do software development and fairly open-ended research activity, users just want to know what you're doing with their machine. They just want information so that they're informed. They may ask why, and be prepared to have that conversation. A lot of times those conversations changed policy decisions in ways I hadn't considered.

Engage your end-users, tell them what you're doing (a blog/wiki/intranet page of some sort is great), and just be approachable. "This is the way it's going to be," is a recipe for a CLM. (Career Limiting Move.)

My suggestion is to find a couple of licensed applications that are in demand and offer them through Self Service. At first Self Service is then just a place for them to get Adobe Creative Cloud, but then as you add more and more functionality it instead becomes a great tool.

Also, if you are going to take the time to make use of Self Service, take the time to upload icons for everything, makes it all so much nicer.

Just wanted to chime in and say I agree with everyone's advice here. I'd even go so far as to invite them to learn more about what the Casper Suite does, what its capable of, what you plan on using it for, and maybe a short list of some other similar environments using it. Your JAMF TAM may be able to help you a little with the last one since they can reach out to other customers similar to yours to see if they'd be willing to have a conversation on how they are using it and what challenges they may have had.
I only say to invite them to learn more because we have a few, err, "colorful" customers here who seem convinced (for reasons that I simply can't fathom) that we use the Casper Suite to spy on them, activate their iSight camera to take images, track their were-abouts and even spy on their browser usage. Not even joking with this. You should see the misinformation out there on it. The main issue is that, its almost human nature that in the absence of information, people naturally tend to make 's#it' up. The more you can nip that in the bud the better off the entire experience will be. Be open and honest and you'll be surprised at how different the whole process will be.

I would also echo @Marker.43's advice on Self Service. Don't overlook it despite the fact that everyone will have local admin rights. You can still make it a very valuable place for them to go for stuff if you do it right, and that will add value and engender buy-in.

This is actually something I get asked a lot, and I wrote up a blog about it here.

The short answer is to use Self Service as your lead selling point. When you tell people you're giving them things, they get excited.

Likewise in echoing @Marker.43 Self Service is by far the easiest way to get visibility of Casper with end users.
Pitch it along the lines of "As soon as we purchase new Software or Hardware we can make them available in Self Service complete and ready to go, no serials, no settings to configure, just press install and then use!".
Also highlight the benefits of improved inventory allowing you to proactively advise/assist users who's machines are out of date etc...

Thanks, all, you've given me a lot to chew on. I will look into the possibility of offering more in self-service, but I am not sure that will be much of a draw for my toughest crowd, the hardcore developers, because they don't want/need Microsoft anything or Adobe anything. They have their own custom set of tools as well as some basic stuff we provide when they start, but I'll run the idea by people who've been here longer than I have to see if there's something there I am missing. One things for sure, this group I mentioned rarely asks for any technical assistance; they are very proficient with their MacBook Pros and are accomplished troubleshooters of all things technical. Laying the program all out on the table is probably the only way to build trust, as they "know too much."
@kitzy -- that blog post looks great, your response to the comment below it, too.

Thanks, everyone!

Ah, developers! Bless their hearts.

My experience supporting developers has taught me two things.

1. They must understand why they're administrators on their Macs. Specifically, so they can install software and make system changes.
    
   They should understand being an administrator does not give them free reign to install pirated or self-purchased software. That's for the company to manage not them. Yes, put licensed software in Self Service and make that the only way they can get the software. Explain this is how you can provide them software on demand and maintain license compliance for the company.

2. Invariably, you'll have one or two developers who are the tape-over-the-camera types. They are paranoid and watch system processes like a hawk. They'll notice the jamf binary taking CPU cycles and will either question it or disable it. Make them aware of this binary and how Casper works. Specifically, Casper uses only built-in OS X software for management. The binary is typically called for an extended period of time when running weekly inventory. Casper is agentless and installs no third party daemons that run all the time.

With that said, it was a developer who paid me the kindest compliment. He said I "manage with a firm hand but a light touch." I thought that was a beautiful way to sum up what I like to think of my Mac management style.