so you are not average joe, are you?

truecrypt doesnt help with "modest got no pgp/mime handling"
truecrypt does not manage your gpg keys.

truecrypt does crypt your filesystem and thats not a solution for average joe (I script that faster as joe installs truecrypt and gets it working, the problem with large crypts is that it drains battery)

to deliver to windows, as mass device you could decrypt a partition setup with truecrypt as it is available for windows (AFAIK) but you need to install it and configure it

summary:
truecrypt (in my eyes) is a standalone solution for encrypting partitions and it makes them also available while in massstorage mode within YOUR windows. (same goes for LUKS I know)


for eCryptfs quiet the same answer apart of I dont know another OS than unix based to work with it