I recently paid 2500 THB for a Camry ride with huahintaxi.com. Very convenient, and they were very responsive to my emails, considering that I basically booked it minutes before getting on the flight from KIX to BKK (plans changed due to Japan quake). I'd not pay for the hotel car given that it's twice the Camry rate.

On the way back we took the hotel shuttle bus for 500 THB per person (thus total 1000 THB), which was a very comfortable Toyota minibus. We were the only pax from Hua Hin to the Bangkok Hyatt (that's where it goes).