I work for a service bureau / design house / large format printer. I started working with InDesign at the beta stage and absolutely adore it. I found that working with a "real" job was the best learning experience - the tutorials are great, but everyone has different needs. The learning curve was pretty quick - there is just a lot more things that InDesign will do but once you find out how, everything is pretty intuitive. We especially like the multi-user license and the fact that the program has so much built in - scaling, shadows, feathering, outlined editable text, convert all text to paths, etc etc. - so add-ons are a bonus, not a necessity.
I love how everything is right there! Tabs and style sheets, etc. can be accessed right from the palette - no constant mousing up to the menu bar, scrolling down, making a change, closing, etc etc.
If you are switching from Quark and don't want to learn new keyboard shortcuts, you can go to "Edit / Keyboard Shortcuts" and set it to "Shortcuts for Quark 4.0". InDesign shortcuts & tools very similar to Illustrator and Photoshop. You can import all your styles, including colour palettes, from another document which saves all sorts of time and aggravation. And pdfing is a breeze since Acrobat is built right in.
Now I only work in Quark if I absolutely have to.