I've discovered that, on my computer at least, LightDM causes crashes very consistently. If I login with LightDM, just touching the ctrl key can cause a crash. If I replace LightDM with LXDM or GDM, this problem goes away. And I'm not the first one to notice:
I don't know how LightDM ever made it out of beta, let along become the default on Ubuntu 11.10. And now this "love" is going to be bestowed on KDE users.
As far as I know there's currently no plans to make LightDM the default DM on KDE and even if that's going to happen it will take time. Well the first distro to use it is probably Kubuntu 12.04 but that again is their own choise.
I personally love the idea. Plasma integration quite simply makes it the most powerful display manager out there.
So far, LightDM is a complete disaster on decent desktop environments I've tried it on.
On the flip side, LightDM is fantastic on the worst desktop I've ever used. (Unity) Hardly a surprise since that's the only thing Canonical is serious about.
At least they didn't try lobbing that trainwreck into Kubuntu 11.10. It's bad enough that it's in Xubuntu, unthemed, with broken power management policy and no automatic login support. I wonder if we will dodge this particular bullet in Kubuntu 12.04. It's probably not that hard to clobber it and go back to KDM. But for crying out loud, quit removing stable functional software from upstream and replacing it with your own version 0.1 garbage heaps. It makes more work for me, the user, to get a system that works right.