I personally don't think doing the HSC on computers is a good idea.
There's no way computers will be appropriate for anything that requires a calculation or uses symbols so it is only really appropriate for subjects like English and History.
The problem with using computers for examination for subjects like English or History is that the student has no incentive to work on his or her handwriting skills and thus their writing speed and legibility declines. Also, when it comes to university exams (which at the moment are handwritten with no proposed changes), that luxury of having a computer in an exam is diminished.
Considering the Board has to block access to everything including internet, spelling/grammar check etc, prevent hackers from infiltrating these blocks or using spyware, as well as ensure that the computers work at the same speed (no computer must lag!) and must work smoothly at all times to ensure a fair examination, would be a nightmare and I reckon it would be way too expensive and ineffective to implement.
I mean, there must be computer access to EVERYONE who takes an exam (that makes potentially 70 000 computers that need to be up, secure and perfectly working for the English exams) but since it's only used the most for English (much less people do other subjects like History), all that effort and cost to get them all running smoothly with very tight security would be almost redundant after the English exams are done lol