iPod questions

[daffodils]

I'm in my late 30's, and thinking of joining the MP3 "revolution" and getting an iPod. I was wondering if folks would be willing to share positives and negatives about the different models. I have a relatively large CD collection, and I'm thinking that it would be easier to travel (which I do for work a lot - driving) with an iPod than a buttload of CD's. Here's the other thing - when I travel, it's always in a rental car, so I'd have to get some sort of transponder-thing to play it in a vehicle, as well as some way to hook it up to my existing entertainment system. (don't want a specific speaker-docking system for an iPod)

Thanks for any and all comments!