TL;DR: Stay here! Dive here! And say hi to JJ for me!
Savusavu was a delight; while my girlfriend and I enjoyed our time on Viti Levu, the small-town feel and laid-back atmosphere of the north island was just the thing we needed. I intend to return to Fiji, and when I do I'll most certainly stay at Daku again.
The first thing to know about Daku is that JJ and Delia, the owners of the resort, are delightful people who will bend over backwards to be accommodating and friendly to you. Our first moments on the island JJ appeared personally at the Savusavu airport (the first airport I've seen with no walls) to drive us to the resort. He was such a delight to chat with, telling us both about himself and about Savusavu, that we arrived in no time.
The resort is a few minutes' drive outside of town, which was a perfect location for what I was looking for: we got the relaxed and quiet atmosphere of a remote location, but could go to town for a $4 and 4 minute taxi ride. (As an aside, Savusavu has an insane number of taxis; literally 1/4 of the cars in town were taxis, which made it incredibly easy to get a ride. Even better, every driver we had was honest and charged us the same reasonable rate.) In addition, Savusavu is a pretty small town; while you'll probably want to go into town for dinner a night or two, there really isn't actually that much to do. You'll be better off relaxing at Daku or heading out on one of the excursions that JJ, Delia, or the any of the alway-helpful staff will help you plan.
The only activity I did while at Daku was scuba diving, and for good reason: the diving in this part of Fiji is the stupefyingly, stunningly, amazing. The Jean-Michel Cousteau dive shop (attached to the resort of the same name), a 10 minute ($8) taxi ride further down the road out of town, is an absolutely world-class operation that took me on the best dives of my life. Even better, staying at Daku saved us money two ways: first, while the Cousteau resort is a very very nice, a bungalow at Daku is 1/5 or 1/10 of the price of a room at Cousteau. Second, Daku's arranged a special rate that make the diving prices very reasonable (not cheap, but a great value for the level of service we got). The relative proximity to Cousteau is another reason that Daku's just-out-of-town was great – every morning the staff would call us a taxi and we'd just have to roll out of our bungalow and we'd be on the boat in 20 minutes.
The other standout thing at Daku was its food. Each night a delicious family-style dinner is served on the patio. Our meals varied across all kinds of cuisines – much more than the other resorts we'd stayed at in Fiji – but were always tasty. If you're committed to private meals you might be skeptical, but we really enjoyed spending a little bit of time chatting with the other guests (even the gaggle of teenage Girl Scouts from America!), something that it's all too easy to miss out on when you're traveling as a couple. I'd always try to sit near JJ or Delia, though, since they reliably made for interesting and funny conversation.
The long and the short of this review is that Daku was a treat to stay at: it had nice rooms, good food, and everyone there made us feel welcome. Enjoy your stay!