There is one missing pioce of info on this thread that affects toe in or no toe in: the off axis reposnse of the speaker itself. If the dispersion is very consistent, across the midrange and tweeter, you can live with less toe in as the off axis sounds pretty much like on axis. But if it varies significantly, say a bullet tweeter and cone midrange, the dispersion varies greatly and this doesnt work especially off axis. The test is pink noise: sit diretly in front and then move off to the side. DIfferent? Or not?
Someone mentioned vertical dispersion and this is important too. You must be on axis with this as the combined output of the tweeter and mid at crossover narrows the vertical dispersion quite a bit.
This horizontal off axis has one other important affect, reflections. If the reflections have a different response than direct/on axis, it can be a mess for imaging. When these on axis ouput and off axis reflections combine you get weird cancellations and the image suffers.
Brad