I am a scientist and I have to read a lot of research papers, scientific documents, mathematical and statistical charts, equations, etc. All these documents are in PDF. No 6" device will adequately display these PDFs. The reflow feature is only good for PDFs that are text-only. Reflow is useless for documents of this type. I will list below the readers that I think are best suited to handle PDFs for this particular usage (academic, technical, and scientific) that have a large display
0. Notebook/netbook - of course, you can always read on them with a full-featured PDF viewer (disadvantages: heavy, short battery life, lack of portability for reading).
1. The iPad - currently best PDF viewer at the portable device level (disadvantages: a bit heavy for my preference and has an LCD screen. I get eye strain from reading on LCD a long time).
2. The Entourage eDGe - good PDF viewer with dual screen support (disadvantages: even heavier than the iPad and not very portable. Difficult to read on it for long periods of time).
3. Kindle DXG - haven't tried this one yet but the PDF support appears to be decent (disadvantages: poor PDF support, many important PDF features missing, slow searches in PDF documents).
That's about it in the current market. In a few months, there will be better devices more suitable for PDF reading.