I'll start at the end - Regardless of what Citrix tells you, don't let the size of your organization dictate whether or not you use VDI in a Box instead of XenDesktop. The real reason for using one or the other should have absolutely nothing to do with the size of the organization or the number of VDI seats. Like choosing any VDI platform, it should be based entirely on use case.
Many conversations I have about VDI in a Box include a discussion about how it's slated for XX number of users. I had conversations with just about anyone who would listen at Citrix Synergy in Barcelona a few weeks ago, and I learned that while Citrix partners are touting VDI in a Box as a sub-500 user solution (or sub-1000, depending who you talk to), in some places in Europe, it's being sold as a sub-50 user solution!
To me, this means that, not only is Citrix conveying the wrong message about how to use VDI in a Box, they're also allowing partners (and possibly themselves) to use arbitrary numbers. That leads to internal competition between two completely separate VDI products. Worse, it means that sales reps and partners are left pushing the wrong product because of higher commission or margin (not that that's anything new), which isn't best for the customer. This kind of confusion is on par with that of Microsoft licensing.
For a few reasons, this all gets me pretty fired up. First, I've always had a soft spot for Kaviza. They've been an underdog with a really tight, simple solution. To see them get acquired just to compete against another product in their new company is not exactly what I hoped for. Second, while I was happy they were acquired by Citrix, it was with the hope that the simplicity of VDI in a Box would rub off a bit on XenDesktop, and that the two would either blend into a single, harmonious product or, at the very least, VDI in a Box would serve as an entry-level VDI product with a clear, easy upgrade path to XenDesktop.
So how can Citrix and its partners get it right?
In the short-term, Citrix can stop focusing on the number of users for the project. Yes, it's a factor, but so many other things come into play before number of users. Things like storage requirements, persistent vs. non-persistent VMs, and the need for FlexCast (which amounts to XenDesktop, XenApp, XenClient, and streamed apps) all come into play just as much.
I mentioned this to a few people, and I was told that this is mainly used as a guideline for the company size to target (SMB for VDI in a Box, enterprise for XenDesktop). To me, this is even more useless, because now we're talking about targeting only sub-1000 person companies for VDI in a Box, and only 1000+ companies for XenDesktop. That means that a company might need XenDesktop or VDI in a Box, but never learn of it because the partner they're talking with leaves it out of the conversation based solely on company size.
Note: I do realize that this is how Citrix can say that the products don't compete against each other. If you say VDI in a Box is only for sub-1000 person companies and XenDesktop is for 1000+ person companies, then there's no competition because they're meant for different areas. As you can imagine, I don't think that's true :)
If you have an environment that doesn't require, say XenClient or XenApp and local storage with non-persistent VM's is ok, then you should absolutely be leaning towards VDI in a Box. Only then should you consider the number of users to see if your specific use case will scale properly. There are implementations of VDI in a Box that go well above 1000 users, so the precedent is already there that it will scale to accommodate the size of the vast majority of VDI deployments in the world.
The opposite is also true. Say you only need fifty users (regardless of company size), but your use case requires XenApp and XenClient, along with built-in App-V support and has high storage requirements. XenDesktop is probably going to be the product for you, even though it falls well below the 1000 (or 500) seat threshold.
So, it all depends on each specific use case, and that, to me, is the responsibility of the partner. Instead of selling the same solution over and over again (which is easy), they need to roll up their sleeves and actually discover the best solution for each customer. The problem is that the information their getting from Citrix is shortsighted at best, and downright misleading at worst.
How can this get worked on in the long term, then? I think Citrix has to get away from having two separate products that, let's face it, compete with each other. The "number of users" limitation is there to draw an arbitrary line between the two so that they can say they don't compete with each other, but that's pretty transparent (or at least it should be now). There are many good things about XenDesktop, but it is a very complex solution (a fact that VMware is very willing to reinforce). VDI in a Box, on the other hand, is perhaps too simple, with scalability concerns about it's grid architecture.
Citrix would do well by trying to adapt the grid architecture to be more scalable (or at least prove its scalability) and incorporate that, along with the ease of standing up new servers, into XenDesktop. XenDesktop can contribute by adding in the FlexCast features and Provisioning Server, which will help the image creation and maintenance processes where VDI in a Box catches some criticism.
There's probably a dozen ways to slice up the two products and repackage them, and it's not an enviable task. I do think, though, that it's a necessary one. Having two products that compete against each other in a niche market cannot be a good thing.
In the meantime, though, I'll bring it home. Forget anything you've heard about what size organizations should be using XenDesktop or VDI in a Box. Bring them both in, and put them through your specific use case. Compare your storage, VM state, application delivery, user base, and scalability requirements to each solution and let that determine which product you use.
For more discussion on this, check out the podcast of the Brian & Gabe Live show that we recorded yesterday at about the 12 minute mark. Desktone's Peter McKay was our guest, and he and Brian shared their thoughts on this as well. They bring up how small business don't want anything to do with owning and running their own VDI environment, let alone deciding on a use case, among other things.