eBook Reader for Datasheets
I've used a Kindle DX to read datasheets, and it has been a relatively pleasant experience. Typically, on a datasheet, the text is reasonably large enough that it looks OK. I've also used it on journal papers, and found that the text is small enough that it can be hard to read. Figures with very fine lines don't show up, but again, datasheets typically aren't too bad about this. 

The zoom ability is limited, which makes it difficult to zoom in just enough to cut out the margins. One workaround is to "print" the PDF using a PDF printer on a smaller virtual page. It might be worth it to figure out the correct settings for something large, like a book or microcontroller datasheet, or for a particular manufacturer you use frequently, but it's a clunky hack.

I don't think I would lay down $480 USD for just reading datasheets. The experience feels second-class compared to the rest of the e-book features. I view it as a nice perk of the device.