The solution given below is not for portable or instant uses. But it's the best solution I've seen for a home or other permanent installation...
Advantages:
- Low cost
- Low tech - you can build it yourself
- Low maintenance
- No consumables like filters to keep replacing
- Tested more than 10 years in the real world
- The main concern I've read is lack of minerals in the water, but you can get easily get the minerals your body needs from other sources, example eating vegetables
- In temperate winters the same method can be powered by fuel
Here are the links:
http://www.epsea.org/stills.html
Presentation with some water quality analysis and cost/gallon:
http://www.epsea.org/borderpact.pdf
10-year test results:
http://solar.nmsu.edu/publications/1437ISESpaper05.pdf
