Take the train and go to Vang Vieng or Luang Prabang (both places have beautiful landscape) as Vientiane is not a nice city. I applied in Vientiane 2 weeks ago. I applied on a Monday and Wednesday I got the interview for the following Monday. I got the DTV approved 1h after the interview, total of 8 days including the weekend. If I didn't have to send a new photo twice, the process would have been even faster!