There's an existing
thread about an experiment I ran, where I tried to put 10,000 books on a Kindle2 - the results would be identical on a DX.
To summarize, the Kindles are not optimized for indexing and searching on large volumes of data (yet). I loaded 5,000 documents and rendered the device pretty much useless. As a follow-up, I would like to try and load a large number of PDFs, since PDFs are not indexed. I would assume that the Kindle will operate fine, but without the ability to search across the PDFs.
As for the find functions, there is another
thread regarding the Kindle's ability to search.
Hope these help - feel free to post any follow-ups.