Let me tell you: it sucks. - Lockscreen disapears when my session is locked, I have to type my password blind..
- Scrolling sucks, plainly. The trackpad registers clicks when I don't want him to, leading to me moving text around when I just want to move the pointer.. it's so unbearable that I brought my old mouse at my job.
- The fan is audible and always on. It also sends the heat back on my left hand (I'm left handed and the vents are on the left of the laptop), which sucks.
- Debian 8 packages don't include Intel acceleration, so you have to use experimental packages. But using them, it results in Skype being impossible to install..
- Did I talk about the miserable battery life? The laptop is brand new (Latitude E5550).
Seriously, you're going to regret it.
I've been running Archlinux myself for the last 2 years and it's relatively painless, some issues with trackpad sometimes but I use a mouse most of the time anyway.
For the lock screen, most of the ones I've used don't have a box to type the password so you have no visual input, like in a terminal. There are some that display it like lightdm that you can install
Biggest complaint by far was trackpad support in Linux. It's a mess out of the box: weird acceleration curves, bad scrolling, twitchy, overly sensitive clicking, the works.
Luckily it's Linux, so it's Configurable™, and with enough tweaking I had a script that would feed a bunch of settings into the userspace synclient synaptics configuration tool, and get a trackpad experience that was mostly bearable. EXCEPT that the damn driver would somehow reset itself randomly every hour or two, and my trackpad would be back to the default mess until the script re-ran.
There were the other common problems too: an update broke X config, font rendering was janky, battery life was a joke. The Alfred replacement I was using would forget its keybinding on every startup. Unity/compiz would stop respecting screen hotcorner triggers until I open the config, cleared, saved, reenabled, and resaved them. Etc, etc, et-fucking-cetera.
It's more or less the same experience I've had on-and-off with Linux on the desktop since 1999. It mostly "works", but it's inevitably death by a 1000 papercuts and after a few months I'm fed up with it and switch to something less grating.
Every now and again I forget about the mess and try again and usually give up after a few days when I start remembering it all. I'm sure some people thrive in that kind of environment but I just need to get work done and when the OS gets in the way of that, it doesn't matter that "you just need to configure ..."