Why do I loose effects when I flatten layers?

I've been working on a poster composed of several groups of layers and probably around a total of 80 layers. When I flatten the image, I loose all of my layer effects, things like bevel and emboss on text get flattened out. What is happening here and how do I fix it?

You must judge your layer effects at 100% magnification. Try this before / after. Any other magnification is just an approximation.

thanks, that is what is happening. If I view the effects where the poster fits the screen, the relative effects look much differently than when I view at 100%.

So my follow-up question is why the effects look dramatically different based on magnification? I realize that they cannot be precise at lower magnification, but it is not even close to being representative between low and full magnification. If a "flattened" version of the lower magnification can be accurate enough, why can't an unflattened version at the same magnification look the same?

I'm guessing it has to do with the complexity of rendering scaled live effects, and the accompanying anti-aliasing. It must be a nightmare just to approximate them. But even with a flattened image, you'll see some differences depending on zoom level. Just remember always to judge at 100% zoom level - for now.