The only boutique hotel I can think of with a pool is the Hotel Palomar. They have an indoor rooftop pool. The Palomar is excellent and I highly recommend it.
3* Atlanta Marietta area hotel Dates: 2/16/13 - 2/19/13 Amenities showing: Free Parking Free Internet Fitness Center Pool(s) Recommendation: still gathering reviews Cost: $49 a night Note: Most other hotels in Marietta are sold out for these dates.
I was hoping for the Palomar but the Hyatt for this price is a respectable deal. Hotwire Listing: 95% Customer Satisfaction BED CHOICE Smoke Free Fitness Restaurant Business Center High Speed Internet