There are plugins both in Chrome and FF where any PDF links automatically opens it up using google docs. Much more faster smoother than native PDF loading. I just tried out this new integrated PDF on Chrome Dev channel (6.0437.1), and as mentioned it doesn't have all the PDF features, it loads PDFs on the left hand corner, instead of center. Much much faster though.

My experience has been that downloading + opening pdfs with a decent pdf viewer is much faster than google docs. I personally use evince, but probably anything other than acrobat would work.

Despite that I share the same experience as btmorex (my native PDF viewer is faster than any web viewer), there is also the additional problem that you need sometimes restricted access to the PDF. I often read journal papers and most of them can only be accessed from inside an University network -- i.e. Google cannot access them (or at least their web PDF reader is not able to load them).