It's the place I intend to go and live when I'm finished with Bangkok. The area has all the things you want, perhaps excluding mountains, and the city itself is easily livable. With the airport and also easy access to Pakse a bonus. Last time was there hired a taxi for the day and did a loop including Pha Taem National Park (excellent) and Sam Phan Bok (Three thousand holes - no, not like Soi 6!) and several nice temples. Good roads, not busy.