The viewfinder does indeed zoom with the lens - I got the camera out to check. It works really well. The only time I notice that the viewfinder and the lens can get out of sync is when you're vey close to a subject (e.g. in a macro situation) and there's parallax. In such (macro) cases it's best to rely on the screen on the back.
Yes, the optical viewfinder does zoom in and out with the lens ... you can also see my review on youtube ... type in the search block kblakney61 and look for my review on my Fujifilm X10 .. thanks .. Ken B.