That situation sounds so familiar (exact same boat I was in). There are a couple of threads in this section about PDF reading on the various top readers. The ultimate verdict: For the 6" readers, PDF rendering isn't that good*, but the Iliad does a decent job at rendering, so you could possibly convert all your books and read them on that machine YMMV.
* - I just bought a sony reader 500 (dipping my toes into the pool) and I just used Sony's conversion tool to try to read a number of my Oreily PDF books. The formatting so far has been alright, but the main problem is the font is too small and way too light to read comfortably. The benefit of the Sony series is that there are a number of converter programs out there, so I am hoping that through fiddling with settings and programs I can fix the font issues and be happy. I didn't buy the reader expecting PDF support to work though (did my research), so this is just a bonus that won't determine if I keep / upgrade e-ink devices.
If you absolutely want a 6" device (I know that's the main reason stopping me from getting an Iliad - too big) I would suggest the Kindle (depending on where you live). The only reason why is that the PDF support on all 6" devices will be off, but the Kindle give you two outs: Browser** and Book Store.
If you are able to find online copies (or post online copies; you are a web dev) then the Kindle browser may be a good alternative to having the books on your actual device. Secondly, Amazon is a very large bookstore, and if I had to put money on which device would see more tech books by the top publishers, my money would be on Amazon. Oreiley, Sams, and the like may open up an independent third party store on their own in the future, but I can see digital copies from them (either directly or through outlets like safari) going with the Amazon DRM for maximum market penetration (even if the number don't reflect that the Kindle is actually the best selling reader).
Might be a long winded answer, but I wanted to pass on all the info I got from my research on the same topic. If you keep up with this site, I will post my findings on document conversion in the Sony Content forum, so you can make a more informed decision.
** - Iliad also has a browser, and has been confirmed that it can read the Safari books site, while the Kindle is unable to.