That is a long way to go to start with, and it is not very easy to get to Guadalcanal, so don't judge its popularity based on the number of responses you get in a short period of time.
My husband and I were on the Bilikiki in June of 2006, and it was - bar none - the most amazing dive trip I've ever taken. The boat was in nice condition, nothing fancy, but a nice liveaboard. the food was amazing, given where we were, and the crew was absolutely wonderful. The managers, Michelle and Monty, were fabulous, though I think they may be taking a break from liveaboard life now (or soon).
The diving was PHENOMENAL. Don't go expecting lots of large pelagics, but the macro life and the hard and soft corals were gorgeous. We did see a single manta and a few sharks (Mary Island), but that isn't what the Solomons are all about...if you like to look for little things, you will be in heaven.
As far as vis goes, we dive most of the time in local San Diego, where more than 20 ft vis is a good day, so the 60-ft vis (on a bad day) in the Sol's didn't really bother me much
[Note - just noticed that's where you're from!!! Let's just say...I think we San Diego divers are happy with any visibility, right????]
We have other places we'd like to go, but I'd go back on the Bilikiki in a heartbeat.
We met a very gracious couple while onboard who happen to be incredible UW photographers; their website includes many trip reports on the Bilikiki, so take a look:
Underwater Photography
Allison