> I'd really love to keep my OS X-style keybindings. It's really frustrating for me to be on Windows and try to paste the system clipboard into a command line. What is it again? Shift-Insert or Control-Insert? And how do I open a new terminal window? Alt-F2?
That should be possible, but it's probably going to require quite a bit of manual fiddling in order to get things to work with the Command key instead of Control for CUA-style bindings. KDE makes this pretty easy, though somewhat tedious through the GUI; all the keyboard shortcuts are managed through the "Shortcuts and Gestures" section of KDE's System Settings.
> The above also goes for Emacs text editing bindings (OS X comes with C-p, C-n, C-k, C-o, C-v, etc.). I want them around too.
Should also be possible through the above-mentioned settings system if you're using KDE. Can't speak for other desktop environments, alas.
> iTerm2. I was sure this wouldn't be a problem, but after looking more into it, apparently ... it is. I've heard that some emulators can't even wrap text properly. I'd also like if it could support profile switching via escape code and other nice things like that.
Konsole (also with KDE) should work nicely for your purposes, though maybe I'm misunderstanding what you're referring to about text wrapping and profile switching (the behavior between iTerm and Konsole regarding text wrapping seems to be identical from what I can tell by a cursory side-by-side check, and Konsole does support multiple profiles).
> Alfred. Not so much for searching for applications, more for having a mini-"command line" that I can use from anywhere.
This depends on what functionality from Alfred you're hoping to still have. KDE's search functionality is pretty comprehensive if that's what you're looking for. It'll also launch programs, even if they're not applications which show up in KDE's menus (i.e. if you type in `xterm`, you'll get a "Run xterm" option that'll - you guessed it - launch xterm).
> Another thing is compatibility. Of course if that was my highest priority, I'd go with Ubuntu and Unity. It seems like more and more things are starting to say "Linux" when they mean "stock Ubuntu". I cannot stand Unity, so I'm thinking Linux Mint. I'm also giving Elementary OS a try in a VM right now, so we'll see how that goes.
Given the above, it sounds like (to me) KDE's going to be a pretty good fit for you. Not only can you customize it to your heart's content to match what you're used to with OS X (and then some), but it's also one of the more full-featured desktop environments.
My normal go-tos for KDE-based distros are openSUSE and Slackware. If you're new to GNU/Linux, openSUSE would be better, but if you already have some server-side GNU/Linux experience (or are very comfortable with the internals of Unix-like operating systems - which seems to be the case if you're dabbling in trying to tweak a Unix as opinionated as OS X), Slackware would be a fun choice (and an excellent learning experience; the common adage - "if you use a Linux distro, you'll learn that distro; if you use Slackware, you'll learn Linux" - is pretty true in a lot of cases).
That said, if compatibility with Ubuntu is your priority, I would recommend Kubuntu, which is literally Ubuntu with KDE instead of Unity. That was my daily driver for awhile before I switched to openSUSE and Slackware, and it worked well.
There's also PC-BSD if you'd rather go with a BSD instead of a Linux. It's definitely the best choice for a desktop-oriented BSD, and it ships with KDE (if I remember right). I haven't tried using it in a long time, though (I usually stick to OpenBSD for my own BSD needs).