We want something central on the beach for 6 nights each that aleeps four. Any recommendations?

Makena Surf (Maui) is a terrific location; but really pricey unless you find a deal (2b/2b $442/nt; maybe VRBO? $350/nt: http://www.vrbo.com/214194)

My favorite on Maui has become the Napili Sunset - up past Kaanapali - and there is a nice grocery store/small shopping center as you turn from the main road. http://www.napilisunset.com/

Years ago - we stayed at a condo and also a B & B down Kiehei/Wailua way - and that is also nice.

On Oahu - you might check out condos over at Kailua - or even B & B's by beautiful Lanakai, or up at Waimea on the North Shore. VRBO is a good source.

Our favorite is Kaanapali Alii on Kaanapali Beach, if you want a resort development. It's a luxury condo, pretty pricey too.

'Central' on Oahu is Waikiki. AFAIK the only condo on the beach is Waikiki Shores.

As for Maui, you'd choose between South Maui and West Maui. South is more convenient for touring to Haleakala and Upcountry, Iao Valley, and Road to Hana. Lahaina/Kaanapali in West Maui is the most densely developed.

We have stayed at the Maui Kai and the Kaleialoha condos as well as our time share. While both were nice, I would rather stay at the Kaleialoha (room 412). It's not quite so high and windy. It's also a bit more centralized and close to the farmers market and grocery. A lot of the pricing and availability will depend on when you're going.

Another consideration, The Aston Mahana next to Maui Kai. I have stayed at both. Both On the water and all oceanfron views facing Lanai and Molokai. View approx same from both, Mahana a step above the Maui Kai and more pricey. Request mid or higher floor. This time I'll be at the Mahana coming up in January

PS, if you want the Kaanapali experience and have the money, Kaanapali Alii is a great choice. Just too pricey for my budget.

My biggest problem with the Aston Mahana is that there is a chain-link fence separating it from the Kaanapali beach path, which is one of my favorite things about Kaanapali!

Assuming by 'central' you mean Waikiki for Oahu, then Waikiki Shores as mentioned above is the only condo building directly on the beach there, I'm pretty sure.