not unless you are printing at a huge scale looking at it with a magnifying glass.

When you save, look at the save options and under compression you can see how the images will be compressed. If you set the resolution of your images to be higher than the actual Tiffs, the Tiffs in the pdf will remain unchanged.

in addition to what garpike said, if you're coming from an application that can handle vectors (cad, indesign, illustrator), and you have something other than pictures in your document, the print quality will actually be better (especially if you uncheck the "compress vector art" box in the same panel garpike mentioned)

for raster images, PDFs use jpeg compression. so it IS a bit lossy.

side note: i really don't mind JPGs for images, but i hate mp3s for their lack of quality. i haven't noticed a significant detriment in JPGs. can someone show/tell me why i should be using tiffs?

The only reason I would consider a tif is that it can maintain photoshop layers within it, thereby negating the need for an additional .psd file.

Our IT guy hates JPEGs hard. He tells us to save our PDFs with ZIP compression, never JPEG. Apprently JPEGs tend to crash plotters.