I use Preview a lot and generally really like it. Since moving from Tiger to Snow Leopard I've also started to use Preview for PDFs, which I didn't do previously. However, I have a couple of annoying issues with it:
1. Opening multiple files simultaneously from the Finder has seemingly random results. Sometimes all files open in one Preview window (as I've directed in Preferences); sometimes only a few of the selected files open at all; and sometimes two Preview windows open, each with some of the selected files. Quitting Preview and reopening the selected files often changes the behaviour.
2. The Zoom button is broken. Admittedly, window zoom has never worked reliably for me in OS X's history, but this is a new problem. If I open a large image file, zoom works fine. But if I open a second file (while the first is still open in Preview) zoom no longer works. Clicking the green zoom button repeatedly causes the window to flap back and forth pathetically between two unwanted sizes.
Anyone else have these issues?