More like 500-2000ms - there are a few commercial codecs (Kakadu - as licensed in OS X, Aware) which are well-polished but the open-source situation was wretched for many years, relying on a few libraries which were indifferently maintained and seriously unoptimized. This meant that there were many valid files which could not be opened, key features like tiled decoding weren't supported and everything is so much slower that users will comment on how much longer it takes simply to open or convert a file.

There is some good news in that OpenJPEG (http://www.openjpeg.org/) has been making significant progress in recent years and is now on track to become an official reference implementation:

https://groups.google.com/d/msg/openjpeg/OMc40gUsBIw/UM1ggXk...

Hopefully this will also translate into continued performance work and robustness testing, which would mean potential hope for a browser other than Safari to add native support:

https://bugzilla.mozilla.org/show_bug.cgi?id=36351#c120