yeah, no kidding, a real bitch if you want to back up your systems, and the hit to processing speed is significant, though with it enabled, the days of popping out a hard drive, and grabbing whatever the hell's on there with a usb connection are over
and i work with dozens of disparate windows systems on multiple hardware platforms on the regular, the speed degradation with bitlocker encryption still exists, and is noticeable
I've supported bitlocker in corporate deployments. I have also spent some time in independent repair shops. I have little confidence in users to supply a bitlocker key, let alone even know what one is. I anticipate a lot of "what? I already gave you my password."
You can still mount it to another machine if you have the key. It's an extra layer of pain in the ass, though.
I don't use an M$ account so if your key is backed up to the cloud (aside: can't wait to read the headline about when that gets breached) I don't personally know offhand how difficult it is to extricate your BitLocker keys from Microsoft.