Chall - the diving is, without question, incredible. If you go, get up to Gizo. Go to this website:
Dive Gizo - Exotic diving in and around the Solomon Islands
Danny is a very cool guy and runs a good outfit. Tell him the Smackster sent you and he'll punch you in the nose.
The Toa Maru is really incredible. One of the best wreck dives I've ever done.
As for safety, the political situation has really deteriorated over the last 10-15 years. But much of that seems to be centered around Guadalcanal and Malaita. Ozi - will have a more current picture on that than I.
We had a few cruisers going through when I was there - and never heard any serious complaints, apart from minor theft, etc. if you left stuff hanging around.
Even so, the Western province was always the more peaceful and easy going area. And that's where the great diving is anyway.
Ozi - I lived on Gnossi Ridge when I was there. Killer view of Iron Bottom Sound and Savo (where I lived for a couple of months for training). You should visit Savo if you get a chance. Incredible place. Just a huge volcano - but great people.