Hi there,
I was there with new newly qualified girlfriend back in April. I'd certainly speak very positively about it. Accom excellent - wonderful to be over the water and reef, we saw all sorts of interesting critters right off our balcony - rays, lionfish, pipefish, various sorts of parrot fish etc. Food was good, and the general dive service is really excellent - good boats, good DMs.
The local house reef is largely artificial, but quite extensive and with some good creatures, and often plays host to large schools of jacks that come in for a visit. We also saw a pregnant ghost pipefish there on our checkout dive (to which I didn't bring my camera - nuts!). The other nearby sites on Mabul island, at the rig (old oil rig turned hotel nearby) and at Sipidan are also really good; mostly small interesting critters, lots of nudis, rays, crocodile fish, I even managed to get close and personal with a peacock mantis shrimp (beware their punch!), and also a fair few turtles, grouper, sweet lips and other slightly larger fish.
The only thing I would say is that if you want to go to Sipidan you may have to be persistent and keep asking the spanish manageress to put you on the list. She says it makes no difference, but I think it can't help. Ask with charm, flirt if needs be, but it's well worth it for the day on the island. We did two dives at Barracuda Point (and two elsewhere) when we were there and two moments will stay with me for ever - floating just on the edge of the sloped reef, at the top of the drop off (which goes down from 20m to something like 600!) and seeing about a dozen white tipped and black tipped sharks cruising past, and also hanging onto the bottom in a saddle with a school of, I would estimate, 1000+ barracudas stretching as far as the vis would allow us to see in front and behind us (and we're talking 20m+ tropical vis here!).
Other thing to note - the night diving is pretty good, the dusk diving even better, but they aren't entirely at ease with people doing it, as the current can be quite strong. However, reassure them you're up to it (if you are!), explain your dive plan and you'll be fine. No more than one per day though.
Biggest negative experience we had was getting there. I think the transfer boat was out of action briefly, so we were basically dumped at a slightly sketchy bar/swimming platform out of town and had about a two hour wait for the transfer. Not really a big drama, but frustrating when you just want to jump in and start diving!
Damn, thinking back on it I'm envious that you've got this all to look forward to! Spare a space in your kit bag?