I own both the PRS-300, 600 & now the Touch 4G. There simply is no comparison; the Touch screen is, by far, sharper and clearer than any Sony reader, including the PRS- 650.
I went to a nearby Sony "Style" store and compared the new PRS-350 and 650 to my collection (PRS-300, 600 and Ipod Touch 4G). The 4G was clearly the best of the lot. Never mind its other superior capabilities, the Apple gadget is the best reader I have seen. Except ---
It is small and those with problems like my friend's macular degeneration cannot use it. It does not have a convenient dictionary, highlighting or anotation capabilities. Also, It does need a recharge after some hours instead of some days. One more thing: all the readers using the eink screen do better in direct sunlight. Still I prefer my new 4G to either of my PRS's in anything but direct sunlight, including bright north-sky shade.
I am a person driven by facts. I, previously, supported the Sony approach to ereaders and may still buy a 650. However, it is clear that the "touch 4G" is superior in every way but those referenced above.