^It should be pointed out that VI is only one segment of socionics. I've found that Socionics has a similar variety of opinions as MBTI. Only one guy owns the socionics.com domain, and while it has some interesting information, not all socionists (as in, the Russian writers/psychologists who specialize in it) agree with him.
The only reason why they didn't just adopt MBTI itself is that it was relatively unknown when Aushra Augusta developed Socionics in the 70's (behind the Iron Curtain, that is).. She was only focusing on Jung. It was until the 80's that she heard of Isabel Myer's. It's funny that it turned out fairly similar and that they were both heading in the same direction. Where the VI idea originally stems from is when one of the more famous writers on the subject (Ekaterina Filatova) interviewed a lot of people over time, she came up with some composite sketches just to capture the general essence or pattern she thought she was detecting in each type. I'm not sure what she was proposing exactly, but I've heard that she doesn't have much to actually say about VI herself. And I would agree with Jim, Wikisocion seems to be a better source. It's user driven, but the basis for most articles or descriptions is from people like Filatova.
Another good site (if you use Google translate) is
http://www.socionics.org. If you click on descriptions for each type, you'll see that there are about 8 or 9 separate descriptions from different authors. It might help to get a better picture.
What throws me off is the subtype theory.. It's kind of hard to sift through the information and tell if I'm more EII or IEI.. or even something else. Heh. I've taken a step back from reading up on it and just stick to MBTI for now.