I recently attempted to use Dreamweaver CS5 for mac. I've used CS3 and 4 on Windows before, and they were fine. A little bloated, but they worked OK.
CS5 on mac is an absolute disaster! It's *so* prone to crashing. It fails to recognise my non-QWERTY keyboard layout for keyboard shortcuts. It doesn't support the usual Mac behaviour for navigating text (e.g. hold command and press left or right to get to the beginning or end of line). The default font is so absurdly small I can't read it. Did I mention that it crashes a lot? Argh, what a piece of ****.
For designing websites, I've found Microsoft's Expression Web to be surprisingly decent, and half the price of Dreamweaver. I know it's not on Mac. Just thought I'd... throw that out there though.