[Mopsa Aspom]

Can you tell me about the speed of the note taking process in PRS-350?
I have the Sony Reader PRS-600 and the time it takes to annotate (generally I just underline interesting passages) increases as I progress in the book, until it becomes despairing.
The weird thing is that even if the disk is almost empty, as I annotate a book, the process gets slower.
Imagine I have just one book of 300 pages in my reader – as I begin reading and annotating, the annotation is quick, but as I progress along the book, the annotation process gets slower, and slower (until it takes about 20 seconds to accept a note). And imagine I have a second book in my reader and, after reading and annotating the first, I pass to the second (without deleting the first book or the annotations from the reader). The same thing happens – at the beginning of the book, note taking is quick, and then it gets slower.
As annotation is very important for me, I’m searching for a good alternative to my PRS-600.