Ola, I would definitely recommend the 300D - I've had mine for about two months and absolutely love it.
Photoshop does keep EXIF data intact except when you "Save for web". This removes both the EXIF data and any embedded preview. I think it also adjusts the the Gamma (on the Apple OS X version I use).
If you are playing with the RAW data from the 300D you either need CS or the RAW plugin for version 7 (and I agree with Brad that CS is a massive step forward for digital photographers).