I think these may all be related to the missing 5-way capability. However, for annotation and highlighting there is the additional issue of how to specify a location in the PDF accurately. Annotations at the page level should be easy to do though. Dictionary access may need more than just being able to select a word, but, on the other hand, the iRex DR1000S allows MobiPocket dictionaries to be used in PDFs.
The DXG has a 5 way controller. It is a little joystick instead of the D Pad on the K3 but it has 5 way capability. That is how you identify words for the dictionary and start highlights and the like in a regular book.