Yes it's good news, mentioned it
back here. Some of the WW1 Diaries have been online for years - 1/5th NF and 1/4th NF, who fought alongside our own guys in the 1/7th. But sods law being what it is they never did the digitisation of the 1/7th but it will be online very shortly as you say.
Of great importance are the embedded field returns, but they haven't digitised those as far as I am aware in their earlier attempts. If they do, the number of pages would expand by an order of magnitude, so I suspect they wont be doing it.
On the subject of the National Archives, I'll (almost certainly now) get the chance end of next month to pop in there for a 5 hour session, so is there anything essential (or just interesting) we need?
NA Search is here:
http://discovery.nationalarchives.gov.uk/SearchUI/