>Other than that, I've yet to hear any substantive reason why I wouldn't use BitLocker.

You shouldn't trust any closed source crypto. Same goes for FileVault.

They're certainly better than nothing, however.

  Other than that, I've yet to hear any 
  substantive reason why I wouldn't use 
  BitLocker.

The thinking goes like this:

1. RSA released software with backdoors, at the behest of the NSA.

2. Therefore, the NSA has the ability to make companies release software with backdoors.

3. The FBI and British governments are known to have asked for backdoors to be included in BitLocker.

4. Therefore, the NSA has the motive to have a backdoor put in.

5. Microsoft have not proved BitLocker /does not/ contain backdoors.

But you have to run Windows on bitlocker.

so you've already handed over your machine no matter what FDE you use.

certainly trusting less people is better than trusting more, since _any_ nefarious third party in this scenario already has the keys to the kingdom.

Full-disk encryption is primarily used to protect offline volumes. If no one can boot your disk, it doesn't matter if Microsoft can upload its entire contents to the NSA once Windows is started. The concern is that a flaw in BitLocker's FDE would make it vulnerable to attacks while the volume is offline.

FDE doesn't really protect online volumes. Yes, the disk is still encrypted, but the OS transparently decrypts any requested sector, so other security measures are necessary to protect mounted volumes.

It's a reference to TrueCrypt being shut down, they are pushing BitLocker. The reason you in theory shouldn't trust closed source encryption solutions is because you have no idea if they have a way to decrypt your data internally. If such a thing were leaked or discovered in the black hat community, your data is now compromised (in theory).

90% of the reason is, IMO, people are just gunshy about all things Microsoft.

Which is kind of funny, really- if you are already running Windows, I wouldn't think it would matter whether you use TrueCrypt or BitLocker. Windows is the proverbial janitor with keys to all the offices. It's a little too late to keep Microsoft out.

I think there are better alternatives available, its security re: NSA etc is obviously questionable just because it is such an enterprise product.