We recently stayed in a 3br/3ba unit in building "B" at Marriott Kauai Lagoons. We are not owners, but rented a week on RedWeek for a good price. This property is a hard one to review actually because there are some definate "Pros" but also some "Cons" as well. Most of the "Cons" aren't really anything Marriott can rectify however.
On the positive side, the rooms are very nice, pretty much brand new, with great kitchens (granite counters and sub-zero appliances etc.), flat-screens and blue-rays in every room. Some of the furniture that was chosen didn't exactly have small children in mind however, for example the coffee table which was a huge inverted pyramid thing with quite sharp pointed metal corners, exactly the type of thing you would child-proof at home with toddlers. Also, it would be nice to have some kind of better locking mechanism or safety latch on the accordian-style doors to the balcony. Our 2.5 yr-old was able to open the locked door and go out to the 3rd floor balcony by himself. Aside from these toddler-proofing safety concerns, the rooms were outstanding.
Also nice was the fact that it didn't seem like many people were staying there, because everytime we used the pool, we were either the only ones using it, or perhaps one other family. It was a welcome change from having to jockey for poolside chairs at other more crowded resorts.
Now, some concerns about the service. First I guess it should be stated that this property is still being fully completed with building "C" not open yet (as of 10/2011). However, the staff is so minimal it is laughable. There is no bell-hop service at all. We pulled up in our rental car with all the luggage that a toddler and 2 adults bring and when I asked for luggage assistance I was pointed toward a luggage cart and told "go ahead you can use it", not exactly my idea of a supposedly high-end resort. There are NO facilities on property, no market, no restaurants, no kids activities, nothing. Just a swimming pool and a shuttle bus which will take you down to the Marriott Kauai Beach Club, however, they are quick to point out that you are not allowed to use their swimming pool or beach chairs, but they will be happy to let you sign Kauai Beach Club food/bev charges to your Lagoons room (they say this like its some kind of great benefit for you).
The real problem with this "resort" is the location. Probably one must understand the history of the whole Kauai Lagoons master project plan as a backdrop. Basically, from what I understand it has been a financial disaster that someone has taken a real bath on. I think Marriott snapped up this Kauai Lagoons parcel for a good price and is trying to make the best of it (I believe they were originally slated to be Ritz-Carlton residences). The problem is, the idea of having these man-made lagoons with boats cruising along the waterways to shops, restaurants and residences has become a far-fetched farce that is years and years away from being realized, if ever. What it is at the moment however, is just man-made swamps that are a mosquito paradise that will eat you alive if you dont take precautions.
There is no beach access from the property, only a shuttle to the Marriott Kauai Beach Club beach (but stay off their chairs and out of their pool!), and the views aren't that great. Right in front of the property are custom residential lots for future resale, with PVC pipes all over them, and just beyond that is the skeleton of an abandoned Ritz-Carlton hotel, literally two stories built and now just abandoned, its looks just awful and Marriott could at least paint some shade of green all the stark white pillars so as to make it more blend into the background. As it is now, it looks like a bombed out building from WWII or something. And just beyond that is the port where container ships come in/out. Our 2.5 yr old loved seeing the "big boats", but we found it odd to have a resort view of loading/offloading container ships in the background.
And then there is of course the proximity to Lihue airport, literally a stones throw. Now, I must say it wasn't a big deal to us (other reviewers had more issues with this) because our 2.5 yr old son was excited everytime a helicopter flew overahead, which is quite literally every few minutes at times. It is true the helicopters take off and fly directly over the hotel on their route, and they are noisy no question about it. Planes coming and going weren't as big a deal, not as noisy.
So all in all, I would say this property has some issues, particularly for families with kids (no beach access, no "water-park" type of pool aside from a small short slide, no other kids activities). But, the rooms are very nice. I think this property is just going to be run more like an apartment complex than a separate resort, with shuttles to take you to the Marriott Kauai Beach Club (but yet even they dont fully welcome Lagoon guests as use of pool/chairs is not permitted).
We spent much of our time away from the property at different beaches and parks in Poipu, Waimea, Princeville, etc. but it was nice to come back to the quality of rooms here, we just wish the property itself could offer more.