Broadly, I agree with
PrismPaul. These types of attempts to broaden debate beyond simple left/right ideologism are useful to that extent, but not much farther. They're not to be taken seriously any more than the kind of relationship quizzes that women's magazines have. If you treat them in the same way, as a bit of fun, they are harmless and they do add a little more shading.
To
Orat, I would say that many of your objections to the placings on the left/right axis seem to me to stem from a peculiarly American perception of what the "left" is i.e. government control of everything. It is not necessarily about government controlling everything in it's ideology, it has only been that in the practical applications of governmental socialism.
For example, a traditional libertarian leftwinger would not necessarily want the
government to control industry - it is more important that the
workers do that. This could be achieved just as easily by making the workers more important in business decision making than shareholders, or actually making them one and the same (by only giving or selling shares to workers).
A whole economy of workers' cooperatives would fufil the socialist desire that ownership of the means of production should reside with workers by hand or brain (a paraphrase of the old Labour Clause IV) without government being involved. Indeed, this type of interpretation of left-wing ideals holds out a great deal more hope in a basically capitalist system that some of the worst excesses of capitalism might be reined in without losing the incentives to innovation and, certainly, without losing competition.
In this context, it is perfectly possible to be a classic left-winger and a libertarian.
A two-axis model like this is more useful than a one-dimensional model (the old left-right spectrum), but it does have limitations, particularly in categorising the likes of Stalin & Hitler, as you point out. People have got around this in the past by saying that if you go far enough in either direction along the simple left/right spectrum, you end up coming round the other side. Hitler and Stalin both took state control of industry, Stalin because it gave "workers" (i.e government) control, Hitler because he wanted a constant state of war, one line of thinking goes. Another is that what we normally call "commmunism" was in fact state capitalism - the workers didn't own anything, and the state owned everything.
Myself, I would argue that whatever their politics, their primary motivation and application of their ideas was through totalitarianism, which is not really related to either axis.
Maybe a third axis of totalitarianism/participation is needed. It's similar to libertarian/authoritarian superficially, but at root is about the level of involvement expected of the people in day-to-day government, rather than the level of interference in daily life expected of the government.
For example, at one extreme, you would have the direct democracy of the ancient Greeks, where every voter was part of the parliament. Moving "down" (if the axis is a vertical "z" axis in a notional 3-D matrix) you'd pass through the kind of government by plebescite becoming more common in EU countries, passing through a wide area of ordinary voter participationthat would typify most democracies, where the only active participation is during elections.
Below the y-x plane, you start to see public participation being ignored or restricted (Florida 2000 anyone?

), then actively discouraged, until you get to true totalitarianism where is simple is not permitted, for example in real or
de facto one-party states (like Saddam's Iraq or Mugabe's Zimbabwe, or even , more benignly, post-war Japan) or where there is no semblance of democracy at all (Nazi Germany, Soviet Russia, China, etc.)
In this model, Hitler and Stalin would both be well below the xy plane.
Edited to add
I just though of a good illustration of the 2D matrix. Authoritarians on both sides generally disapprove of drugs, prostitution, gambling, and so on, so tend to call for bans on them or resist legalisation. Libertarians say "do what you will" and aruge that people should be allowed to do what they want.
A right-wing libertarian sees taxes as theft by government, but a left wing libertarian would allow drug use, prostitution, etc, but would
tax them to both raise revenue for their spending ideas and to discourage the behaviour, which few people actively approve of, libertarian or not.