Well, since then I sold my Apple display and bought a 25-inch Dell Ultrasharp, which is a great replacement without the Apple vendor lock-in. So, I tried Ubuntu again (15.04) on dual-boot, following the same instructions as before, more or less. Everything's been fine. I've been using Ubuntu as my day-to-day OS for a couple of weeks now, and slowly transferring files across.
Lookin' good so far. And, more to the point, FLOSS (Free Libre Open Source Software).
