What the DX lacks is what every other e-reader lacks when it comes to reading pdfs: the screen to too small. A truly great pdf reader would have a letter size or A4 size screen so that panning/zooming etc. would be completely unnecessary. Unfortunately, there are no e-readers with large screens. The DX is the closest thing you'll find right now.
You can use the DX to read pdfs and I find that by rotating the device to landscape orientation the magnification that is automatically applied to fill the width of the screen is just about right for reading any pdf. However, tables and illustrations are often cut-off, so it isn't an ideal solution. There is no support for TOC or active links and I think highlighting/notes don't work on pdf files either, though I have never tried.
You can add Duokan to your device to improve pdf handling a bit, but in the end it really comes down to screen size and there's nothing you can do about that.