Thanks. Sounds like most agree splitting the island trip into the north and south shore is the best. I'll take that advice and go that route then. My fiance has never been to Hawaii, so I figured Oahu is a must in there. Besides, I already have booked the airfare to/fr Honolulu.

Questions: How would you split it? 2:2, 3:1, 1:3? Should I go north first then south or south first then north shore?

As far as activities/itenary, I see doing most of them in the north shore area. Here is what I am thinking for a 4 nights/5 days trip.
Day 1: Fly into Kauai, drive to north shore stopping by some water falls
Day 2: Na Pali Coast hike (1/2 day), Kee Beach (1/2 day)
Day 3: Haena/Hanalae beach (1/2 day), St Regis hotel pool/beach (1/2 day)
Day 4: Drive to south shore (Grand Hyatt) in morning, spend afternoon in the Hyatt swimming pool/lagoons.
Day 5: Fly back to Honolulu

OR
Day 3: Haena/Hanalae beach (1/2 day), drive to south shore in the afternoon.
Day 4: Spend the day at Hyatt pools/lagoon and spa

OR
Day 1: Fly into Kauai, drive to south shore, spend the night at Hyatt pool/lagoon area
Day 2: Hyatt in the morning, drive to St Regis in the afternoon
Day 3: Na Pali Cost and Kee Beach
Day 4: Haena/Hanalae beach (1/2 day), St Regis hotel pool/beach (1/2 day)
Day 5: Fly back day

What do you think? (Sorry to change the subject a bit, but it is related.)