I recently switched to Mac and already I've found great design apps. Here's some quick reviews:
Coda is an app made for designing websites. It's very simple in its user-interface, while still being very feature-filled(actually the UI won an Apple Design award). You can create "sites" and include the ftp information for that website, so that once you've finished creating it, uploading it to the server is just a few clicks away.
When coding in (x)HTML, there's syntax coloring, auto-complete for tags and attributes, and a preview mode that uses WebKit to show you exactly how the page will look in Safari.
The CSS section also includes features that save time. You have the option of coding by hand, or using a GUI for generating the CSS properties and values.
Another great feature is the built-in designer references. There's information about HTML, CSS, JS, and PHP.
Pixelmator is a program for graphic design. It's a great Photoshop alternative, for only $59. It integrates with the Mac OS very well, giving you features such as using the iSight camera to take a picture of yourself or dragging photos straight from iPhoto into a new layer.
The user-interface isn't close to the UI for Photoshop. It's actually closer to Mac's UI. The dialog windows are a translucent black and they blur out what's behind it, giving a dark glassy look. There's an option to work in fullscreen, so the background turns black and only the Pixelmator windows are visible. This can easily be found by hitting the "f" key or selecting the fullscreen icon on the tools menu.
A great thing about Pixelmator is it's fast. A full start up takes literally around 1 second. Graphics processes are done on the GPU, so your CPU usage is low leaving space for other apps.
