When I turned it on (be aware - not ALL versions of Windows have it - for example Windows 8.1 Pro and Enterprise - I am assuming the same for Windows 10), all went as planned but the system was really slow for a 16GB machine. While I was just setting it up (installing Office, etc.), the system was really bogged down. I let it sit for a day then installed some other things - same issue.
This was really beginning to concern me about the long term performance until I noticed that in the System Tray, the BitLocker icon was there. Right clicking on it is showed "Encrypting". Being a new system with a 1TB drive, I assumed it would take a while so I let it sit for a full day. Checked the status, same deal so wasn't sure if it was stuck or some other major issue.
Looking around for some answers (I obviously didn't want to reboot), I finally found the command line method for managing BitLocker (manage-bde). While this command has a lot of options (locking/unlocking a drive, etc.) it has the option to simply check the status. Open a Command Window (running As Administrator!), enter the command:
Viola! It shows the complete information you'd want to know:
Disk volumes that can be protected with
BitLocker Drive Encryption:
Volume C: [drive name]
Size: 930.79 GB
BitLocker Version: 2.0
Conversion Status: Encryption in Progress
Percentage Encrypted: 73.8%
Encryption Method: AES 128
Protection Status: Protection Off
Lock Status: Unlocked
<some more info about type of key, etc. here>
<other drives will be listed here>
In short, enabling BitLocker means being very patient. In the case of my drive (930.79 GB), it took over two and a half days to complete!