It's quite heavy for me (too much for my liking as well) - Chrome 27 on OSX.
The culprit is http://shkspr.mobi/blog/?custom-css=1&csblog=1&cscache=6&csr... giving a font-weight of 500. Probably affecting OSX people only
that said: if you have a screenshot of your browser w/ the font showing and what desktop env+browser you're in, I can probably tell you what's wrong.