They've been displaying pdfs as text for some time but it was very ugly — just enough to quickly see what's inside. “Quick preview” is new feature. They render pdfs but have raw text too for convenient copy/paste.

Google's reader should be much more light and perform faster, esp. in old browsers with slow DOM implementation. The disadvantage of this solution is non-native (for client) text rendering. Also things like embedded video and scripting would not work, but I think Scribd is not supporting those either.

So, not at all the same thing. Whoever downvoted you have some explaining to do.

No user cares or even knows that it's an image vs something else. As long as you can select the text etc it's exactly the same.