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Still bad IMO. I do not recommend using an e-reader for PDFs. I use a Kindle DX on a rare occasion.

A tablet computer with pen provides the best experience IMO. I've used a iPad and an Android tablet before. Both have excellent PDF reading software. I recommend Bookari on Android. The Microsoft Surface, however, beats everything else I've tried.

I'm on a paperwhite (the newest, I think?).

Honestly, I think it works quite well. Code is fine. Graphics / Illustrations might be bad at times, depending on the formatting job.

But then .. you know .. if you want an ebook reader, I'd consider this ~300 bucks one too expensive.

Not great -- the screen is too small, though the high DPI helps a bit. IMO the iPad is the only way to go for technical PDFs. The iPad Air 2 is a magnificent device.