I'd like to hear from TrueCrypt users who've had both good and (if any) bad experiences with it: Is it reliable enough for business-critical use? In my case, I expect to use file-based containers rather than encrypting entire partitions.
For me the nightmare scenario is: I go to open the container, supply the right authentication information (whether it's a passcode, a key, whatever), and TrueCrypt just can't open the container for whatever reason. Perhaps there was a write error on the last update. Perhaps a stray cosmic ray hit just the wrong part of a data structure. Perhaps the machine I last used the container on was destroyed by a falling satellite and I'm now trying to open the container on a different machine with a different architecture (Windows 32-bit instead of *nix 64-bit, whatever). You get the idea.
I don't care about horror stories of lost keys or what-have-you; nothing without a backdoor can protect you from doing something dumb. I'm talking about the software actually failing in a way that loses your data.
(And yes, obviously, if I'm dealing with business-critical data, I'm going to keep backups of the container — multiple point in time going back days/weeks/etc. — to mitigate the effects of some of the above.)