This question turns up a lot, on the irc channel, mailing lists, forums, your local Stammtisch and at weddings. The correct answer is: this is the wrong question. And I'll explain why in this post. Note that I'll be skipping over a couple of technical bits, if you notice those then you're probably not the person that needs to ask the question in the first place.
On your current Linux desktop, right now, you have at least three processes running: the X server, a window manager/compositor and your web browser. The X server is responsible for rendering things to the screen and handling your input. The window manager is responsible for telling the X server where to render the web browser window. Your web browser is responsible for displaying this post. The X server and the window manager communicate over the X protocol, the X server and the web browser do so too. The browser and the window manager communicate through X properties using the X server as a middle man. That too is done via the X protocol. Note: This is of course a very simplified view.
Wayland is a protocol and it replaces the X protocol. Under Wayland, you only need two processes: a compositor and your web browser. The compositor is effectively equivalent to the X server and window manager merged into one thing, and it communicates with the web browser over the Wayland protocol. For this to work you need the compositor and the web browser to be able to understand the Wayland protocol.
This is why the question "is wayland ready yet" does not make a lot of sense. Wayland is the communication protocol and says very little about the implementation of the two sides that you want to communicate.
Let's assume a scenario where we all decide to switch from English to French because it sounds nicer and English was designed in the 80s when ASCII was king so it doesn't support those funky squiggles that the French like to put on every second character. In this scenario, you wouldn't ask "Is French ready yet?" If no-one around you speaks French yet, then that's not the language not being ready, the implementation (i.e. the humans) aren't ready. Maybe you can use French in a restaurant, but not yet in the supermarket. Maybe one waiter speaks both English and French, but the other one French only. So whether you can use French depends very much on the situation. But everyone agrees that eventually we'll all speak French, even though English will hang around for ages until it finally falls out of use. And those squiggles are so cute!
Wayland is the same. The protocol is stable and has been for a while. But not every compositor and/or toolkit/application speak Wayland yet, so it may not be sufficient for your use-case. So rather than asking "Is Wayland ready yet", you should be asking: "Can I run GNOME/KDE/Enlightenment/etc. under Wayland?" That is the right question to ask, and the answer is generally "It depends what you expect to work flawlessly." This also means "people working on Wayland" is often better stated as "people working on Wayland support in ....".
An exception to the above: Wayland as a protocol defines what you can talk about. As a young protocol (compared to X with 30 years worth of extensions) there are things that should be defined in the protocol but aren't yet. For example, Wacom tablet support is currently missing. Those are the legitimate cases where you can say Wayland isn't ready yet and where people are "working on Wayland". Of course, once the protocol is agreed on, you fall back to the above case: both sides of the equation need to implement the new protocol before you can make use of it.
Update 25/01/15: Matthias' answer to Is GNOME on Wayland ready yet?