Layered Tiffs (since Photoshop CS at least) using the TIFF-6 spec can save -EVERYTHING- a PSD file can save including layers, channels, paths, transparecy, etc. The only limitation to TIFF-6 is a max file size of 4 gigs/file...but it can save out images larger than the 30,000 limits of PSD files.
For larger images, the only format is PSB files that can store up to 300,000 pixels.
Layered Tiffs may not be supported by -ALL- tiff readers (although recent ones should) and some of the compression options such as zip compression may not be compatible with 3rd part tiff readers (such as ImagePrint) but -THEY- should be encouraged to fix that!