Is there an e-ink reader with a 8.5"x11"/A4 screen that'll display PDFs? All I want is to be able to bring all my tech ebooks with me to work and be able to look things up/brush up on things on the commute/flight etc.

How is the PDF reading experience?

It's actually quite good if you "root" the device and install koreader[1](the original developer is the same guy who wrote the vnc viewer for kindle, that was mentioned in this thread), or its librerator fork[2]. In contrast to Amazon's practically unusable PDF reader, these open source projects support custom zoom levels, 2-column mode for academic articles etc. Another option is to use k2pdfopt[3].

[1] https://github.com/koreader/koreader

[2] https://github.com/kai771/kindlepdfviewer/tree/librerator

[3] http://www.willus.com/k2pdfopt/