I have a PocketBook Pro 912, exactly for the use case described. Works like a charm. Large screen, A4 PDFs are easy to read. Problems are rare (under heavy use for well over a year I found just one extremely heavy PDF that basically caused the reader to hang, I couldn't even reboot it - that's it, no other problems). I don't even connect it to a computer (why waste desk space?), I just use a microSD card. My collegue has a 911 and connects it all the time, so that seems to work just as well.
Also useful during commute - e-books work very well (Adobe DRM is supported if you want it), built in sudoku is also fun, heh.
Highliting (with the highliter tool) sucks - on most PDFs it's ridiculously slow. BUT: there is another tool, pencil. That works just fine, so instead of highliting I just circle or underline the important parts - besides, it's better than highliting, because you can make handwritten notes. That's very useful. In fact, I rarely highlight anything in texts I just read, I use this while reviewing papers, theses of my students, etc. Marking corrections is very easy in this way.
In other words - a good choice in my opinion.
One important drawback though - you can't export (or print) a PDF with your markings. This really sucks. I heard you can export individual pages as bitmaps, but I haven't tried this. So, if you're going to mix using this with paper versions or with working on a computer... you have a problem. I can live with this, but if you really need this - well, I found where the notes are stored, so you could probably export them somehow, reverse engineer the format (maybe it's trivial?) and find a way to overlay it on the PDF. Maybe it's a solved problem, I didn't really look.
Anyway, if anyone found a way to do this easily, please reply, I'd love to know. Just not so much so to search for solutions. Lazeeee...
Or maybe someone knows a reader as good as this one but with this problem solved. So far I haven't found one that had an e-paper screen - and that's a showstopper. I'm not going to recharge my reader every day or even every week. (*)
(*) If you're going to connect it to a PC almost every day anyway to swap PDFs, you may want to rethink your priorities - you might not really need e-ink, just a large battery, as long as it recharges over USB. Since I rarely do this (microSD!), recharging is a separate task for me. Of course, there are other things to consider - e-ink refreshes slowly, but is better for the eyes - my eyes at least...