I've just downloaded JSON #817 and given it a quick try around a few pages on the BBC News site - nothing strenuous. I noticed that the CPU temperature (BeagleBoard xM RO5.19 16/05/12) was staying around its upper range even after I had closed the browser window so I used TaskUsage to see what might be causing this and found Netsurf using around 80-85% of the CPU even without any browser windows open, just idle on the icon bar.
I reverted to the last version I have to hand (#812) and went round the same pages and closed the window and the CPU usage by NetSurf dropped back to 0% as expected. I understand that being a test version there may be reasons for this, but thought I'd mention it in case it wasn't expected behaviour. -- Grahame Parish